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Two convex lenses with power 2 dioptre are kept in contact

Two convex lenses with power 2 dioptre are kept in contact with each other. The focal length of the combined lens system is

0.10 m
2 m
4 m
0.25 m

Which statements about the refractive index of a material medium

Which one of the following statements about the refractive index of a material medium with respect to air is correct?

It can be either positive or negative.
It can have zero value.
It is unity for all materials.
It is always greater than one.

Which is the natural phenomenon based on which a simple periscope works

Which one of the following is the natural phenomenon based on which a simple periscope works?

Reflection of light
Refraction of light
Dispersion of light
Total internal reflection of light

A myopic person has a power of -1.25 Dioptre. What is the focal length

A myopic person has a power of -1.25 Dioptre. What is the focal length and nature of his lens?

50 cm and convex lens
80 cm and convex lens
50 cm and concave lens
80 cm and concave lens

Splitting of a beam of white light into its constituent colours

Which one of the following processes explains the splitting of a beam of white light into its constituent colours?

Polarization
Dispersion
Diffraction
Reflection

A real image

Consider the following statements:

A real image

can be formed on a screen
is always magnified and inverted

Which of the statements given above is/are correct

1 only
2 only
Both 1 and 2
Neither 1 nor 2

An optician prescribes a power = -0.5 dioptre

An optician prescribes a power = - 0.5 dioptre. The corresponding lens must be a

convex lens of focal length 2 m
concave lens of focal length 50 cm
concave lens of focal length 2 m
convex lens of focal length 50 cm

If the speed of light in air is 3 x 108 m/s, the speed of light in glass

If the speed of light in air is 3 x 10⁸ m/s, the speed of light in glass (with refractive index 1.5) would be

4.5 x 10⁸ m/s
1.5 x 10⁸ m/s
2 x 10⁸ m/s
3 x 10⁸ m/s

While looking at the image formed by a convex lens

While looking at the image formed by a convex lens (one half of the lens is covered with black paper), which one of the following will happen to the image?

Half of the image will be visible
One can see an image of smaller size
Intensity of the image will be diminished
Image will be inverted

A person standing in front of a plane mirror approaches the mirror

A person standing in front of a plane mirror approaches the mirror by 40 cm. The new distance between the person and his image in the plane mirror is

60 cm
1.4 m
1.2 m
2.0 m

An optical illusion which occurs mainly in deserts

An optical illusion which occurs mainly in deserts during hot summer is based on the principle of

Reflection
Interference
Dispersion
Total internal reflection

A rainbow is produced due to which one of the following phenomena

A rainbow is produced due to which one of the following phenomena?

Dispersion of light
Interference of light
Diffraction of light
Scattering of light by atmospheric dust

Concave mirror is used in headlights of vehicles, because it

focuses light from the bulb onto nearby vehicles
sends parallel rays
fits well into the shape of the headlight
is cheaper than other mirrors

The mirrors used as rear-view mirrors in vehicles are

concave
convex
cylindrical
plane

How long does light take to reach the Earth from the Sun

How long does light take to reach the Earth from the Sun?

About 4 minutes
About 8 minutes
About 24 minutes
About 24 hours

The focal length of the eye lens increases when eye muscles

are relaxed and lens becomes thinner
contract and lens becomes thicker
are relaxed and lens becomes thicker
contract and lens becomes thinner

When light rays enter the eye, most of the refraction occurs at the

crystalline lens
outer surface of the cornea
iris
pupil

The bluish colour of water in deep sea is due to

the presence of algae and other plants found in water
reflection of sky in water
scattering of light
absorption of light by the sea

Which phenomena contributes significantly to the reddish appearance of the sun

Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?

Dispersion of light
Scattering of light
Total internal reflection of light
Reflection of light from the earth

The clear sky appears blue because

blue light gets absorbed in the atmosphere
ultraviolet radiations are absorbed in the atmosphere
violet and blue lights get scattered more than lights of all other colours by the atmosphere
light of all other colours is scattered more than the violet and blue colour lights by the atmosphere

Twinkling of stars is due to atmospheric

dispersion of light by water droplets
refraction of light by different layers of varying refractive indices
scattering of light by dust particles
internal reflection of light by clouds

Which phenomena of light are involved in the formation of a rainbow

Which of the following phenomena of light are involved in the formation of a rainbow?

Reflection, refraction and dispersion
Refraction, dispersion and total internal reflection
Refraction, dispersion and internal reflection
Dispersion, scattering and total internal reflection

At noon the sun appears white as

light is least scattered
all the colours of the white light are scattered away
blue colour is scattered the most
red colour is scattered the most

A person cannot see distinctly objects kept beyond 2 m

A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power

+ 0.5 D
– 0.5 D
+ 0.2 D
– 0.2 D

A full length image of a distant tall building

A full length image of a distant tall building can definitely be seen by using

a concave mirror
a convex mirror
a plane mirror
both concave as well as plane mirror

Rays from Sun converge at a point 15 cm in front of a concave mirror

Rays from Sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed so that size of its image is equal to the size of the object?

15 cm in front of the mirror
30 cm in front of the mirror
between 15 cm and 30 cm in front of the mirror
more than 30 cm in front of the mirror

Magnification produced by a rear view mirror fitted in vehicles

is less than one
is more than one
is equal to one
can be more than or less than one depending upon the position of the object in front of it

A light ray enters from medium A to medium B

A light ray enters from medium A to medium B as shown in Figure.

The refractive index of medium B relative to A will be

greater than unity
less than unity
equal to unity
zero

A 10 mm long awl pin is placed vertically in front of a concave mirror

A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is

– 30 cm
– 20 cm
– 40 cm
– 60 cm

Which can make a parallel beam of light when light from a point source

Which of the following can make a parallel beam of light when light from a point source is incident on it?

Concave mirror as well as convex lens
Convex mirror as well as concave lens
Two plane mirrors placed at 90° to each other
Concave mirror as well as concave lens

Two mirrors A and B are placed at right angles to each other

Two mirrors A and B are placed at right angles to each other as shown in Figure.

A ray of light incident on mirror A at an angle of 25° falls on mirror B after reflection. The angle of reflection for the ray reflected from mirror B would be

25°
50°
65°
115°

A small hole P is made in a piece of cardboard

A small hole P is made in a piece of cardboard. The hole is illuminated by a torch as shown in Figure. The pencil of light coming out of the hole falls on a mirror.