X Refraction and Reflection :FA-Test Paper Solved

CBSE PHYSICS CLASS X        Very short Answer

1. What is radius of plane mirror?
Ans: Infinity
2. What is angle of reflection for a ray falling normally on a plane mirror?
Ans: 0
3. Why do we use convex surface for side view mirror?
Ans: Convex mirror always form virtual, smaller and upright image of object for vide range.
4. Can a virtual image be photographed?
Ans: yes.
5. What is the power of a plane mirror?
Ans: 0 because focal length is at infinity
6. When the angle of incidence is 90 , what is the angle of refraction?
Ans: 0 degree
7. What is the value of refractive index of air?
Ans: 1. {The ratio of the sines of the angles of incidence and refraction will be the same if the medium is the
same.}
8. What is the magnification produced by a plane mirror?
Ans: Plane mirror cannot magnify image and has magnification 1 because height of image formed is equal to
that of object.
9. Define power. Give its S.I unit?
Ans: power of a lens is d ability of a lens to converge or diverge an incident rays of light. it is defined as the
reciprocal of its focal length d = [1/f(m) ] Dioptre . Its S.I unit is Dioptre.
10. What is power of sun glass?
Ans: sun glasses do not converge or diverge rays of light hence have no power.
11. Between which two points related to a concave mirror should an object be placed to obtain on a screen
an image twice the size of the object? [2010]
Ans. Between centre of curvature and the principal focus.
12. What are the two factors on which the lateral displacement of an emergent ray from a glass  slab
depends ? [2011]
Ans. (i) Angle of incidence (ii) Thickness of glass slab
13.What is the minimum distance between an object and its real image in case of a concave mirror ? [2011]
Ans. Zero, when object is at centre of curvature, its real image is also formed at the same point.
14. Why do we prefer a convex mirror as a rear-view mirror in vehicles?
Ans. It is because, it covers a wide rear field and forms small, erect and virtual image, close to the eye of the
driver of the vehicle.
15.. Convex mirrors are commonly used as rear-view mirrors in vehicles. Suppose you are sitting in a parked car, you notice a jogger approaching towards you in the side view rnirror.The radius of Curvatureof the side view mirror is 2cm, lf the jogger is running at a speed of 5m/s,how fast the image of the jogger appears to move when the jogger is 9m away from the mirror?
Ans: Radius of curvature C =2cm ; f=c/2 = 1cm = .01m
speed of jogger=5m/s
dist of the jogger from the mirror ,u=9m
image distance at the begining=
1/v + 1/u = 1/f
1/u- 1/f = -1/v
1/v = 1/f - 1/u
=1/9 - 1/-.01
v =9/901m
image distance after 1 sec. the jogger would have moved 5 m.
u=9-5=4m
f=-.01m
1/v = 1/f - 1/u
=1/4 - 1/-.01
v = 4/401m
speed of the image of the jogger =distance / time
dist. = 9/901 - 4/401
t = 1s  
speed = (9/901 - 4/401)m/s=0.00995 m/s=0.01 m/s
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Floatation: Previous Year s’ Questions of 3 marks for class IX

1. An object is made to fall from different heights 20 cm, 40 cm and 60 cm on wet sand.

 (a) What do you observe on the sand?  (b) Explain the reasons of the observations. CBSE Questions

2. A solid object of mass 50 g and volume 100 cm3 is put in water. Will the object float or sink? Give reasons for your answer.

3. Name the instrument used to determine the density of liquid in which balance and graduated cylinder are not required. Why this instrument is made heavy near the bottom?

4. A sphere of mass 5 kg and volume 2.2 × 10^–4 m3 is completely immersed in water. Find the buoyant force exerted by water on the sphere. Density of water = 1000 kgm^–3. (Given: g =9.8m/s²)

5. What happens when :(a) Buoyant Force exerted by the fluid is less than the weight of the body?

(b) Buoyant Force exerted by the fluid is equal to the weight of the body?

6. What is Relative Density? The relative density of a substance is greater than 1, w hat does it signify?

7. If relative density of aluminum is 2.7 and density of water is 1000 kg/m³. What is the density of aluminum in SI unit?

8. The volume of a solid block is 300 cm³, find the mass of water displaced when it is immersed in water? (Density of water is 1 g/cm³)

9. (a) A floating boat displaces water weighing 6000 N.

(i) What is the buoyant force on the boat?  (ii) What is the weight of boat?

(b) What happens to the buoyant force as more and more volume of a solid object is immersed in a liquid?

10. (a) Define relative density.

(b) Relative density of gold is 19.3. The density of water is 10.3 kg/m3. What is the density of gold in S.I. units?
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Class 6th Fun with magnet CBSE /NCERT Questions with answer

CBSE NCERT Class VI Science Lesson 13:Lesson 13: Fun with Magnets.

1. Who discover magnet?

Ans: A Greek shepherd named Magnes discovered magnets 4,000 years ago in Magnesia, Greece. The name magnetite has been derived from Magnesia or Magnes.

2. What is magnet?

Ans: Any material that attract iron object is called magnet. The two ends of a magnet are called its poles. The poles of a magnet are named as the North Pole and the South Pole. In order to identify the poles, the North Pole is usually painted in red colour. All magnets have two poles, and they are called dipoles.  Law of magnets :Unlike poles attract each other and like poles repel each other.

3. Why magnet called load stone?

Ans: Magnet in the form of a bar was used to find directions on the earth, and so it is called as a Lodestone.

4. What are magnetic material and Non-Magnetic Materials?

Ans: Materials that are attracted by a magnet are called magnetic materials. Objects made of materials such as iron, cobalt and nickel are magnetic objects. Examples of magnetic materials include iron nail, key, metal spade, needle and metal door handle.

Materials that are not attracted by magnets are called non-magnetic materials. Examples of non-magnetic materials include rubber, coins, feather and leather.

5. What are different types of magnets?

Ans: Bar magnets : In these magnets, the poles are located at the ends of the bar.

Cylindrical magnets:  In these magnets, the poles are located at the two circular ends of the cylinder.

Horseshoe magnets : In these magnets, the poles are located at the two free ends of the 'U' shape.

6. What is Compass?

Ans: A compass is an instrument that is used to find the directions. It has a thin magnetic needle supported from a pivot so that it can rotate freely. The needle is placed over a dial with the directions marked. The entire assembly is placed inside an airtight box.

7. How can you make artificial magnets?

Ans: A rectangular iron bar, an iron needle, a blade or an iron nail can be turned into a magnet by rubbing a bar magnet over like combing hair to make artificial magnets.

8. How do you protect magnets from losing their magnetic properties?

Ans: Precautions to protect magnets from losing their magnetic properties are:

(a) Never drop magnets from heights. (b) Never heat a magnet. (c) Do not hammer a magnet.

9. Write some use of magnet?

Ans: debit cards, credit cards or ATM cards, audio and video cassettes etc

10. What are magnetic keepers?

Ans: A soft iron pieces placed across the ends of a pairs of bar magnets to preserve the magnetism for a long time is called magnetic keepers.

Class VI Physics: Chapter: Electrical circuit

Quest Time CBSE NCERT VI Chapter: Electric currents, Circuits, Cell.

1. From where do we get electricity?

Ans: A power station provides electricity. If the supply of electricity may fail we use other sources of energy like torch at home.

2. Why does the bulb glow switch on a torch?

Ans: It glows because the electric energy stored in the electric cells is converted into light energy by the bulb.

Hence Electric cell is a source of light energy.

3. Name the scientist who developed first Cell?

Ans: The first electric cell was developed by an Italian scientist Luigi Galvani and then improved by Alessandro Volta.

4. Name a cell that is recharged by Light of The Sun?

Ans: alkali cells and solar cells. Solar cells convert light energy into electric energy.

5. What is an electric cell?

Ans: An electric cell is a device which converts chemical energy into electric energy.

The cell has two different metal plates – one is the positive terminal and the other is the negative terminal. These plates are kept inside a chemical called electrolyte. One of the chemical is white in color NH₄Cl (Ammonium chloride) and other is a black powder MnO₂ (manganese dioxide).

6. What is an electric current?

Ans: Electric current is the flow of electrons or charge. The cell is a source of electric current.

7. What is an electric circuit?

Ans: An electric circuit is the closed path along which electric current flows from the positive terminal to the negative terminal of the battery.

A circuit generally has:

a) A source of electric current - a cell or battery(A group of cell called battery)

b) Connecting wires for carrying current.

c) A device which uses the electricity - a bulb ( Bulb is a device that convert electrical energy into light)

d) A key or a switch – A component of circuits that stop or allow the flow of current. When the current flows the circuit is said to be closed circuit.  When the current does not flow, the circuit is said to be open circuit.

8. How does a bulb glow and produce light?

Ans: Inside the bulb there is a thin coil of wire made of tungsten, called filament. It gets heated and glows when the current flows. Hence, electric energy is converted into light energy by a bulb.

9. If the filament inside the bulb is broken will the bulb glow? Why?

Ans: The circuit is not complete; current does not flow through the circuit and the bulb does not glow.

10. Why do we feel warm when we touch the lighted bulb?

Ans: The bulb also emits heat energy along with light.

CBSE Class 6th Light Shadow and Reflections

LIGHT , SHADOWS AND REFLECTIONS Hots Questions

1. In a completely dark room, can you see your face in a mirror? Why?

Ans: Due to absence of light In a dark room. Light is the source that illuminates our face by reflection.

2. Why cannot we see upside down image of the sun?

Ans: Object like sun is in infinity whose image form point sized or highly demised.

3. Why shadows are black in colour?

Ans: It is because no light reaches on screen in area where shadow form. The colour of object is colour components of light that reflect and reach our eyes.

4. Can you see an object through a “T” shaper pipe? If, no, Why?

Ans: No, it is because light always travel in straight path that is known as rectilinear properties of light.

5. Can you see a reflected light directly? If, no Why?

Ans No, the path of the ray of light is itself invisible but make the things visible only when fall on our eyes.

6. What is the reason for the formation of shadow?

Ans: The rectilinear propagation of light .Kinds of shadow depends on the source f light.

(a)Point source of light form only dark and sharp shadow called the Umbra

(b)Extended source of light (smaller than object) form two reason a dark umbra and another less dark region called penumbra.

(c)Extended source of light (larger than object) : The size of umbra decreases and penumbra increases as screen move away from object and vice versa.

7. How can you see the thing around yourself?

Ans: We see the thing around us when light from a luminous object (like the

Sun, a torch or an electric light) falls on these objects and then travels towards our eye after refection. 

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CBSE ADDA: CBSE Class 6th Light Shadow and Reflections:
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10th Human Eyes ,Reflection and Refraction Numerical CBSE Test Series

10th Human Eyes ,Reflection and refraction Numerical CBSE Test Series

1. An object 5.0 cm in length is placed at a distance of 10cm from a convex mirror of radius of curvature 150cm. Find the position, nature and size of the image.

2.Find the position, nature and size of image of an object 4cm high placed at a distance of 10 cm from a concave mirror of focal length 20 cm.

3.An object is placed at a distance of 25 cm from the pole of a spherical mirror which forms a real, inverted image on the same side of object at 37.5 cm from the pole. Calculate the focal length of mirror and find nature of the mirror.

4.An object 2.0 cm in size is placed 20.0 cm in front of a concave mirror of focal length 10.0 cm. Find the distance from the mirror at which a screen should be placed in order to obtain a sharp image. What will be the size and nature of the image formed?

5.Find the position of an object which when placed in front of a concave mirror of focal length 20 cm produces a virtual image, which is twice the size of the object.

6.A concave lens has a focal length of 15cm. At what distance should an object 10 cm long be placed so that it forms an image of 10 cm from the lens? Find the nature and size of the image formed.

7.A convex lens has a focal length of 30 cm. Calculate at what distance should the object be placed from the lens so that it forms an image at 60 cm on the other side of the lens. Find the magnification produced by the lens in this case.

8.A concave lens has focal length 20cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed.

9.A Calculate the focal length of convex lens which produces a virtual image at a distance of 25 cm of an object placed 10cm in front of it.

10.A concave lens of focal length 15 cm forms an image of 10 cm from the lens. How far is object from the lens? What are its characteristics?

11.Light enters from air into glass plate which has a refractive index of 1.5. Calculate the speed of light in glass. (Given, speed of light in vacuum is 3 x 108ms-1

12.A person cannot see distinctly any object placed beyond 40 cm from his eye. Calculate the power of the lens which will help him to see distant object clearly.

13. The near point of a hypermetropic person is 75 cm from the eye. What is the power of lens required to enable him to read clearly a book held at 25 cm from the eye?

14.A person with a myopic eye is not able to see beyond 3 m distinctly. Determine the nature, focal length and power of the lens required.

15.The near point of a hypermetropic person is 1m. What is the power of lens required to correct this defect? Assume that near point of the normal eye is 25 cm. 10th Light Reflection and refractions : Related Posts Links Light Reflection and refractions Key Concepts Light Reflection and refractions  Study Note CBSE Test Paper Series -1 CBSE Test Paper Series -2 CBSE Test Paper Series(Numerical) -3 CBSE Test Paper Series(Numerical) -4 CBSE Test Paper Series(Solved) -5 CBSE Test Paper Series(MCQ,S) -6 CBSE Test Paper Series (FA-3 Quiz) -7 CBSE Sample Paper Series -8 CBSE Test Paper Series(Solved) -9 CBSE Test Paper Series(Solved) -10

CBSE Class:IX Work Power and Energy Questions and Solution

Q.1. Can any object have mechanical energy even if its momentum is zero? Explain.

Yes, mechanical energy comprises of both potential energy and kinetic energy. Zero momentum means that velocity is zero. Hence, there it no kinetic energy but the object may possess potential energy.

Q.2. The potential energy of a body is 39600J. How high is the body if its mass is 20kg?

The potential energy of a body = mgh

h = PE/mg = 39600j/20kg x9.8m/s²=198m

Q.3. A force of 20 N displaces a body through a distance of 1 m at an angle of 60° from its own direction. Calculate the amount of work done.

Here, force F = 20 N, displacement, s = 1 m. Angle between force and displacement 60°.

Work done,W =Fscos0 =20 X 1 X cos60°=20X 1 X 1/2 = 10J.

A man of 50 kg jumps up to a height of 1.2 m. What is his potential energy at the highest point?

The potential energy of man = mgh = = 50 + 10 X 1.2 J = 600 J

Q.4. How much work is done by a force of 10 N in moving an object through a distance of 4 m in the direction of the force.

Work done Force x Displacement =F.s = (10 N) x (4 rn) = 40 joule or 40J.  
CBSE ADDA: Read more

IX Physics Chapter: Work Power and Energy

9th Work, Energy and Power CBSE Test Paper    9th Work, Energy and Power CBSE Guess Paper IX Work, Energy and Power Study material Download File Work, Energy And Power-CBSE Questions with solution by jsuniltutorial

IX Floatation Physics: Very Short answer Questions

IX Floatation Very Short answer Questions (1 Mark)

1. Give reason why, a block of plastic when released under water comes up to the surface of water.

Ans: It is because of buoyancy force

2. Define density. What is the SI unit of density?

Ans: Mass per unit volume of a substance is called density.

The SI unit of density is kg/m3 or gm/cm3

3. Name and define SI unit of pressure.

Ans: Pascal or n/m2

1 Pascal is the pressure act when 1 N  force acts perpendicular on unit area.

4. What do you understand by the term buoyancy?

Ans: Tendency of fluid to exert an upward force when a body is immersed in to it is called buoyancy

5. Why does a mug full of water feel lighter inside water?

Ans: a mug full of water feels lighter inside water because of buoyancy force

6. A perpendicular force of 50 N acting on a surface generates a pressure of 250 Pa. Calculate the area of cross-section of the surface on which pressure is acting.

Ans: p = F/A Þ A = F/p Þ 50 N/250 Pa = 0.2 m2

7. What is a lactometer used for?

Ans: lactometer used for finding purity of milk

8. State the unit of density and relative density in SI system.

Ans: The unit of density is  kg/m3

There is no unit of relative as it is ratio of same physical quantity.  

9. State Archimedes’ principle.

Ans: When a body is immersed partially or completely in a fluid (liquid or gas), it experiences an up thrust or buoyant force which is equal to the weight of the fluid displaced by the body.

10. What is meant by buoyant force?

Ans:  if a body is immersed partially or completely in a fluid, it experiences an up thrust called buoyant force.

11. A cork floats while the nail sinks in water. Give reason.

Ans: Weight of cork is  less than buoyant force acting on it so it floats Where as : Weight of the nail  is  more than buoyant force acting on it so it sink

12. What is the principle of floatation?

Ans: A body floats is a liquid if weight of the liquid displaced by the immersed portion of the body is equal to the weight of the body.

13. A body of mass 400 g has a volume of 300 cm³. Will body sink in water or not? [Density of water = 1000 kgm–3]

Ans:  density of body =m/v= 400/300=1.3gm/cm3 which is greater than density of water 1gm/cm3

Hence, Body will  sink in water.

14. When we stand on loose sand, our feet go deep into the sand. But when we lie down on the sand our body does not go that deep in the sand. Why?

Ans: when we lie down on the sand our body exert same force on large are that reduce pressure and our body does not go that deep in the sand.

15. Why is it easy to walk on sand with flat shoes, then with high heel shoes?

Ans: flat shoes exert force on large surface area and less force act on sand this make easy to walk on sand