Light

Question 1

What is reflection of light?

Answer 1

The phenomena of bouncing back of light after falling on a plane surface.

Question 2

What are the laws of reflection of light?

Answer 2

1. The angle of incidence is equal to the angle of reflection.
2. The incident ray, normal and reflected ray all lie on the same plane.

Question 3

What is refraction?

Answer 3

The phenomena of bending of light when it enters from one medium to another.

Question 4

What is refractive index?

Answer 4

The ratio of velocity of light in a vacuum to its velocity of light in that medium.
( c / v )

Question 5

What is Snell’s law?

Answer 5

The ratio of sine of angle of incidence to the sine of angle of refraction is always constant i.e. μ= sini / sinr

Question 6

What are the laws of refraction?

Answer 6

1.The ratio of sine of angle of incidence to the sine of angle of refraction is always constant
2. The incident ray refracted ray and normal all lie on the same plane.

Question 7

Where do all the parallel lines meet in concave mirror?

Answer 7

In the focus

Question 8

What happens to the incident ray when it is incident at the pole of concave mirror or convex mirror?

Answer 8

It reflects back making the same angle with principle axis.

Question 9

What happens to the incident ray when it is reflected through the center of curvature of concave mirror?

Answer 9

It reflects back along the same path.

Question 10

The incident ray and their respective refracted rays in a concave mirror are?

Answer 10

Center of curvature - reflects back
At the focus - Parallel
Parallel - At the focus
Pole - pole ( making the same angle )

Question 11

A concave mirror only forms virtual image when?

Answer 11

The object is between pole and focus.

Question 12

The position of object and its corresponding size of the image of concave mirror are :

Answer 12

Beyond C: Image is smaller than the object.
At C: Image is same size as the object.
Between C and F: Image is larger than the object.
At F: No image (image at infinity).
Within F: Image is larger and virtual.

Question 13

Can convex mirror form enlarged image?

Answer 13

No

Question 14

Can convex mirror form real image?

Answer 14

Yes, only when the object is virtual

Question 15

The characteristics of image formed by plane mirror are?

Answer 15

1. Virtual, erect and behind the mirror
2. Laterally inverted
3. Size of object = Size of image
4. Distance between the image behind the mirror is same as the distance of the object from the mirror.

Question 16

Uses of concave mirror are?

Answer 16

By dentists, headlight of vehicles, solar furnaces, shaving mirror

Question 17

Uses of convex mirror are?

Answer 17

Vehicle side mirrors, ATM and security mirrors. (due to greater range of view)

Question 18

What is the radius of curvature and focal length of plane mirror?

Answer 18

0 So, the power of plane mirror is infinite

Question 19

What is glancing angle?

Answer 19

The angle made by the reflecting surface and the incident ray is glancing angle.

Question 20

You can see your image on a mirror but not on plain paper. Why?

Answer 20

A mirror reflects light, while plain paper absorbs it.

Question 21

What is the least distance between real image and real object in a concave mirror?

Answer 21

The least distance between a real image and a real object in a concave mirror is 4 times the focal length of the mirror.

This occurs when the object is placed at the center of curvature of the mirror. In this configuration, the real image is formed at the same distance from the mirror as the object, but on the opposite side

Question 22

Why does a plane mirror reverse left and right but not top to bottom? Explain on the basis of physics.

Answer 22

while it may seem like a plane mirror physically reverses left and right, it is actually our brains that create this illusion to match our usual perspective. The mirror simply reflects the light rays in a predictable way, and our brains interpret the resulting image based on our prior experiences and expectations.

Question 23

Law of rotation of light :

Answer 23

On keeping the direction of incident ray the same, the angle of rotation of the reflected ray is two times the angle of rotation of the plane mirror.

Question 24

What is lateral shift?

Answer 24

The horizontal displacement of ray of light as it crosses the boundary between two media with different refractive indexes is lateral shift.

Question 25

What is the radius of curvature, focal length and power of plane mirror.

Answer 25

The radius of curvature and focal length of a plane mirror is infinite. So, the power is zero

Question 26

If a person moves towards a plane mirror with velocity v in a direction making an angle of theta with the normal of the mirror. The magnitude of the velocity of image relative to the person is?

Answer 26

2vcos theta

Question 27

What is concave mirror?

Answer 27

• The mirror whose reflecting surface is made from the interior surface of a sphere.

Question 28

What is convex mirror?

Answer 28

• The mirror whose reflecting surface is made from outer part of the sphere.

Question 29

What does refractive index measure?

Answer 29

-It measures how much speed of light is decreased in that medium compared to speed of light in vacuum.

Question 29

Under what condition, a spherical mirror becomes a plane mirror?

Answer 29

If u = -v

Question 30

Refractive index for red light and violet light?

Answer 30

Red light - Lowest
Violet light - Highest

Question 31

What is critical angle?

Answer 31

The angle of incidence in the denser medium for which the angle of refraction in the denser medium is 90 degrees is critical angle.