CBSE 10th PHYSICS NATURE OF LIGHT & REFLECTION
Properties of Light:
(a) Under normal
circumstances - Light:. traveling through a uniform medium in a straight line. This properties is
called rectilinear properties of light. Path along with light pass are
called rays. A bunch of rays constitute a beam of light.
However, the following
phenomena can change the path or nature of the light.
(i) Absorption : Light falling on an object may be absorbed, transmitted, or reflected.
(i) Absorption : Light falling on an object may be absorbed, transmitted, or reflected.
(ii) Reflection : Those surfaces which
reflect the most light appear white, or silver. A highly polished, smooth and
flat silver surface acts as a mirror, reflecting a perfect image of the
world around it.
(iii) Refraction : Light that is
transmitted through a medium will usually be deviated somewhat from the
straight path it was previously following. Refraction is an important
characteristic of lenses that allows them to focus a beam of light onto a
single point. Refraction occurs as light passes from a one medium to another
when there is a difference in the optical density between the two materials.(b) . Wave/Particle
Duality : Light may be regarded as a flood of particles,
called photons, or as a wave. In either case, it carries energy through a
vacuum at a velocity which is a universal physical constant, and is the same
for all observers and for all colors. Light frequently behaves as a particle.
(c) Speed of light : The speed of light in vacuum is a universal constant (3 x 10^8 m/s). It is the same for all frequencies of light. The colour of light depends on the frequency of light. Different colours of light travel with different speeds in all other mediums except vacuum. The wavelength of visible light lies in the range of 4μm - 7μm.
The Reflection of Light:
Incident Ray: A ray of light falling on a reflecting surface is called incident ray.
Reflected ray: A ray of light reflected by the reflecting surface is called reflected ray.
Point of Incidence: It is a point on the reflecting surface where a reflected ray and incident ray meet.
Normal : A perpendicular drawn on reflecting surface at the point of incidence is called normal.
Incident angle: The angle drawn in between incident ray and normal.
(c) Speed of light : The speed of light in vacuum is a universal constant (3 x 10^8 m/s). It is the same for all frequencies of light. The colour of light depends on the frequency of light. Different colours of light travel with different speeds in all other mediums except vacuum. The wavelength of visible light lies in the range of 4μm - 7μm.
The Reflection of Light:
Incident Ray: A ray of light falling on a reflecting surface is called incident ray.
Reflected ray: A ray of light reflected by the reflecting surface is called reflected ray.
Point of Incidence: It is a point on the reflecting surface where a reflected ray and incident ray meet.
Normal : A perpendicular drawn on reflecting surface at the point of incidence is called normal.
Incident angle: The angle drawn in between incident ray and normal.
Reflected
angle: The angle drawn in between reflected ray
and normalLaws of reflection:
1. Angle of incidence = angle of reflection
2. The incident ray, reflected ray and Normal are coplanar.
1. Angle of incidence = angle of reflection
2. The incident ray, reflected ray and Normal are coplanar.
Image: A point where an
object appears to be, because the rays from any given point on the object have
been bent so that they come back together and then spread out again from the
image point, or spread apart as if they had originated from the image .
Real image: A point where an object
appears to be, because the rays from any given point on the object have
been bent so that they come back together and then spread out again from
the new point.
Virtual Image: A point where an point object appears to be, because the rays from any given point on the object have been bent so that they spread apart as if they had originated from the point.
An extended object contains many points and the image of the extended object contains the images (real or virtual) of all the object points.
Virtual Image: A point where an point object appears to be, because the rays from any given point on the object have been bent so that they spread apart as if they had originated from the point.
An extended object contains many points and the image of the extended object contains the images (real or virtual) of all the object points.
Image characteristics
Plane mirrors:
Images formed by plane mirrors are
• virtual (for real object)
• upright
• left-right reversed
• the same distance from the mirror as the object's distance, and
• the same size as the object.
Lateral Inversion: The exchange of right and left side of an object and its image is called lateral inversion.
Spherical mirrors:
A spherical mirror is one whose reflecting surface is a part of a hollow sphere. The spherical mirrors are of two types : concave mirror and convex mirror.
Concave mirror: Mirror which is silvered from outer side and the reflection takes place at the inner (concave) surface.
• upright
• left-right reversed
• the same distance from the mirror as the object's distance, and
• the same size as the object.
Lateral Inversion: The exchange of right and left side of an object and its image is called lateral inversion.
Spherical mirrors:
A spherical mirror is one whose reflecting surface is a part of a hollow sphere. The spherical mirrors are of two types : concave mirror and convex mirror.
Concave mirror: Mirror which is silvered from outer side and the reflection takes place at the inner (concave) surface.
Convex mirror: Mirror which is
silvered from inner side and the reflection takes place from outer (convex)
surface.SPHERICAL MIRRORS –
DEFINITIONS
Center of curvature (C): is the center of the sphere whose curvature would be identical to that of the mirror; therefore the center of curvature would be at the center of the sphere that the mirror would form if the mirror curved all the way around.Focal point (f): The point through which all light rays coming into the mirror parallel to the axis would reflect through, or appear to have reflected from.The mirror (principal) axis: The line which passes through the pole (vertex), the center of curvature, and the focal point. It is normal to the mirror at its pole (vertex).
Center of curvature (C): is the center of the sphere whose curvature would be identical to that of the mirror; therefore the center of curvature would be at the center of the sphere that the mirror would form if the mirror curved all the way around.Focal point (f): The point through which all light rays coming into the mirror parallel to the axis would reflect through, or appear to have reflected from.The mirror (principal) axis: The line which passes through the pole (vertex), the center of curvature, and the focal point. It is normal to the mirror at its pole (vertex).
Pole (vertex): The centeral point
on the the mirror surface.
Aperture: The width of the reflecting surface is called aperture.Focal length: The distance of separation between the pole and the focus is called focal length.Rules for drawing ray diagrams:
1. Light incident parallel to the axis will be reflected through the focal point
2.The reverse of this is true, also. Light passing through the focal point will be reflected parallel to the axis
3. Finally, light striking the vertex will be reflected at an equal angle to the axis.Nature of the image
Position of object at ∞ : Nature of the image: Image is real point sized at focus.
Position of object; Beyond C: Nature of image: Image is inverted, small and in between C and F.
Position of object at C Nature of image: Image is inverted, same sized at C
Aperture: The width of the reflecting surface is called aperture.Focal length: The distance of separation between the pole and the focus is called focal length.Rules for drawing ray diagrams:
1. Light incident parallel to the axis will be reflected through the focal point
2.The reverse of this is true, also. Light passing through the focal point will be reflected parallel to the axis
3. Finally, light striking the vertex will be reflected at an equal angle to the axis.Nature of the image
Position of object at ∞ : Nature of the image: Image is real point sized at focus.
Position of object; Beyond C: Nature of image: Image is inverted, small and in between C and F.
Position of object at C Nature of image: Image is inverted, same sized at C
Position of object in between C and F : Nature of image: Large in size,
inverted, beyond C
Position of object; At F : Nature of image: Image is at infinity. Highly enlarged and real
Position of object; At F : Nature of image: Image is at infinity. Highly enlarged and real
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Light Reflection and Refraction Study E-Note Download File
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Derivation or Proof-of-Mirror and Lens formula Download File
Assignment-Physics, Reflection and Refraction Download File
Derivation or Proof-of-Mirror and Lens formula Download File
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