Light Test

Result

Light Test - 9

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Weekly Quiz Competition

Question 1
1 / -0

When an ultraviolet radiation is incident on a surface, no photoelectrons are emitted. If a second beam causes photo-electrons to be ejected, it may consist of

A
radiowaves

B
infrared rays

C
visible light

D
X-rays

Solution

When an ultraviolet radiation is incident on a surface, no photoelectrons are emitted. If a second beam causes photoelectrons to be ejected, it may consist of X-rays.
Question 2
1 / -0

A red cross on a white background, when seen through a red filter,

A
will appear as red cross on a white background

B
will appear as red cross on a black background

C
will appear as black cross on a red background

D
will become invisible

Solution

A red cross on a white background, when seen through a red filter, will become invisible.
Question 3
1 / -0

A bird flying high up in air does not cast shadow on the ground because

A
the size of bird is smaller than sun

B
the size of bird is smaller than earth

C
light rays fall almost normally on the bird

D
birds reflect light

Solution

A bird flying high up in air does not cast shadow on the ground because the size of bird is smaller than sun.
Question 4
1 / -0

A man is 170 cm tall. He wants to see his full length image in a plane mirror. If his eyes are at a height of 164 cm from the ground, minimum length of the plane mirror should be

A
85 cm

B
82 cm

C
170 cm

D
164 cm

Solution

To see full length image in a plane mirror, the minimum length of the mirror should be half the length of the object.
Question 5
1 / -0

Which of the following capital English letters does not show lateral inversion?

A
N

B
O

C
P

D
Q

Solution

O does not show lateral inversion.
Question 6
1 / -0

An object is placed between two plane mirrors inclined at an angle to each other. If the number of images formed is 7, then the angle of inclination is

A
15⁰

B
30⁰

C
45⁰

D
60⁰

Solution

n = - 1
7 = (360/) - 1

= 45⁰
Question 7
1 / -0

In a looking mirror or a window pane, you find that your face appears larger than normal. The mirror or window pane is

A
plane mirror

B
concave mirror

C
convex mirror

D
none of the above

Solution

In a looking mirror or a window pane, you find that your face appears larger than normal. The mirror or window pane is concave mirror.
Question 8
1 / -0

If the angle of incidence is equal to the critical angle, the angle of refraction will be

A
0^o

B
45^o

C
90^o

D
180^o

Solution

If the angle of incidence is equal to the critical angle, the angle of refraction will be 90^o.
Question 9
1 / -0

Time taken by a ray of light to travel through a glass slab of thickness 4 cm and refractive index 1.5 will be

A
2 10^–12s

B
2 10^–10 s

C
2 10^–8s

D
2 10^–11 s

Solution

1.5 = 3 x10⁸/4 x 10^-2 x t
t = 2 x 10^-10 sec
Question 10
1 / -0

A convex lens of focal length 1 metre is placed in contact with another concave lens of equal focal length. What is the focal length of the new lens formed?

A
0

B
+ 2 m

C
+ 1 m

D

Solution

Focal length foe convex lens = 1 m
Focal length for concave lens = - 1 m
Total focal length = 0 m
Power = 1/0 =
Question 11
1 / -0

A thick lens has less focal length. Its power is

A
less

B
more

C
zero

D
infinite

Solution

If we have a thick lens, it has less radius of curvature. The lesser the radius of curvature, the lesser the focal length of the lens.

As the focal length is less, power of the lens will be more.
Question 12
1 / -0

A fly is sitting on the objective of a telescope pointed towards the moon. What effect is expected in photograph of the moon taken through the telescope?

A
The entire field of vision is blocked.

B
There is an image of the fly on the photograph.

C
There is no effect at all.

D
There is a reduction in the intensity of the image.

Solution

There is a reduction in the intensity of the image.
Question 13
1 / -0

A microscope has an objective of 5 mm focal length and eyepiece of 30 mm focal length, and the distance between the lenses is 150 mm. The magnification is

A
50

B
100

C
200

D
250

Solution

Given data:
f_o = 5 mm, focal length of the objective
f_e = 30 mm, focal length of the eye-piece
L = 150 mm, distance between the lenses

The far point magnification power of microscope,
Question 14
1 / -0

The deviation produced by a prism is

A
same for all wavelengths

B
greatest for red and least for violet

C
greatest for violet and least for red

D
not possible

Solution

The deviation produced by a prism is greatest for violet and least for red.
Question 15
1 / -0

A beam of white light after passing through a prism produces a spectrum with seven colours. This is because

A
the prism converts white light into the light of seven colours

B
the prism disperses white light into constituent components

C
the colours are produced by the screen

D
there is no colour but an optical illusion

Solution

A beam of white light after passing through a prism produces a spectrum with seven colours. This is because the prism disperses white light into constituent components.
Question 16
1 / -0

When sunlight enters the earth's atmosphere, the rays which get scattered the most are

A
violet and red

B
yellow and green

C
red and orange

D
violet and blue

Solution

When sunlight enters the earth's atmosphere, the rays which get scattered the most are violet and blue.
Question 17
1 / -0

Water is transparent to visible light while water drops in air are opaque, because

A
fine drops of water are opaque in visible light

B
most of the light is scattered and hence, apparent opacity

C
fog affects our vision adversely

D
the light rays suffer total internal reflection and cannot reach the eye of the observer

Solution

Water is transparent to visible light while water drops in air are opaque, because most of the light is scattered and hence, apparent opacity.
Question 18
1 / -0

The twinkling of stars is due to

A
the fact that stars do no emit light continuously

B
frequent absorption of starlight by their own atmosphere

C
the fact that refractive index of the earth's atmosphere fluctuates

D
intermittent absorption of starlight by earth's atmosphere

Solution

The twinkling of stars is due to the fact that refractive index of the earth's atmosphere fluctuates.
Question 19
1 / -0

If a person uses spectacles with concave lenses, he is suffering from

A
myopia

B
hypermetropia

C
astigmatism

D
cataract

Solution

If a person uses spectacles with concave lenses, he is suffering from myopia.
Question 20
1 / -0

Cylindrical lenses are used to correct the defect of

A
myopia

B
hypermetropic

C
presbyopia

D
astigmatism

Solution

Astigmatism is a condition that causes blurred vision. It occurs when the cornea is irregularly shaped, or sometimes because of the curvature of the lens inside the eye. Cylindrical lenses are used to correct the defect of astigmatism.