PHYSICS [3 Mark Question Answer]

The parallel beam of light on reflection by a concave mirror converges at a point on the principal axis, midway between pole and the centre of curvature. This point is called the principal focus

A ray of light is the path along which light travels.

Since the angle of incidence = 60°.
From the diagram, the Angle of reflection to the normal = angle of incidence to the normal = 60°.
So, the angle between the incident ray and reflected ray = Angle of incidence + Angle of reflection = 60° + 60° = 120°.

Given, a distance of boy from the mirror = 3 m
(a). The distance of the image from mirror = distance of boy from the mirror = 3 m
Distance between a boy and his image = distance of boy from the mirror + distance of the image from mirror = 3+3 = 6 m
(b). Now, a distance of boy from the mirror = 4 m
The distance of the image from mirror = 4 m
Distance between a boy and his image = distance of boy from the mirror + distance of the image from mirror = 4+4 = 8 m.

Angle of reflection to the normal = angle of incidence to the normal = 20°
So the angle between incident ray and reflected ray = Angle of incidence + Angle of reflection = 20 + 20 = 40°

A parallel beam of light is the beam in which rays of light travel parallel to each other. A divergent beam of light is the beam of light in which rays of light diverge from each other as the beam progresses

The image of an object placed at a long distance in front of a convex mirror is formed at principal focus. The radius of the curvature of convex mirror is 20 cm.
The focal length of the convex mirror = radius of curvature/2.
Focal length of convex mirror = 20/2 = 10 cm.
So the image will form at a principal focus 10 cm away from the pole.

We know when the incident ray is parallel to the principal axis then they appear to diverge from a point F.
Geometrically we can find this value and this comes to 2 cm. Centre of curvature = 4 cm.
Focal length = centre of curvature/2.

Focal length =25 cm.
Object distance = 20 cm.
Height o f object = 10 cm.

The image is virtual, erect, and diminished.

Focal length =25 cm.
Object distance = 20 cm.
Height o f object = 10 cm.

Image is virtual, erect, and magnified.

Periscope is used to see over the top of an obstacle. It is also used in submarines for observing for movement of ships. It can be used from the trenches for observing the movement on the surface of the earth.

Given, a distance of boy from the mirror = 3 m
(a). The distance of the image from mirror = distance of boy from the mirror = 3 m
Distance between a boy and his image = distance of boy from the mirror + distance of the image from mirror = 3+3 = 6 m
(b). Now, a distance of boy from the mirror = 4 m
The distance of the image from mirror = 4 m
Distance between a boy and his image = distance of boy from the mirror + distance of the image from mirror = 4+4 = 8 m.

Reflection obeys the following two laws.
a. The incident ray, the reflected ray, and the normal at the point of incidence, all lie in the same plane.
b. The angle of incidence and the angle of reflection are always equal. According to these two laws, this ray will deviate like this:

a. Plane Mirror

b. Convex Mirror

c. Concave Mirror

You can distinguish between a concave mirror and a convex mirror without touching them. When you look into these mirrors by bringing your face close to each mirror, they will produce an image of your face of different types.
A concave mirror will produce a magnified image of your face.
A convex mirror will produce a Diminished image of your face.

You can distinguish between a plane mirror, a concave mirror, and a convex mirror without touching them. When you look into these mirrors by bringing your face close to each mirror, they will produce an image of your face of different types.
A plane mirror will produce an image of the same size as your face.
A concave mirror will produce a magnified image of your face.
A convex mirror will produce a Diminished image of your face.

Linear magnification is defined as the ratio of the height of the image to the height of the object. It is taken to be positive for an image to be virtual and erect and negative when the image is real and inverted.
Magnification produced by a concave mirror is:
Magnification = height of image / height of object.
It is a pure ratio and does not have any units.

Linear magnification is defined as the ratio of the height of the image to the height of the object. It is taken to be positive for an image to be virtual and erect and negative when image is real and inverted.
Magnification = height of image / height of object.