Light Test

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Light Test - 10

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Weekly Quiz Competition

Question 1
1 / -0

To get three images of a single object, one should have two plane mirrors at an angle of :

A
$$60^{\mathrm{o}}$$

B
$$90^{\mathrm{o}}$$

C
$$120^{\mathrm{o}}$$

D
$$30^{\mathrm{o}}$$

Solution

The number of images formed of two plane mirrors are placed at an angle $$\theta$$ is $$\displaystyle \mathrm{n}=\frac{360^{\mathrm{o}}}{\theta}-1$$

Here $$\mathrm{n}=3$$.

$$\Rightarrow \ 3=\displaystyle \frac{360^{\mathrm{o}}}{\theta}-1$$

$$\Rightarrow \theta =\displaystyle \frac{360^{\mathrm{o}}}{4}=90^{\mathrm{o}}$$
Question 2
1 / -0

Two plane mirrors are inclined to each other such that a ray of light incident on the first mirror $$(M_1)$$ and parallel to the second mirror $$(M_2)$$ is finally reflected from the second mirror $$(M_2)$$ parallel to the first mirror $$(M_1)$$. The angle between the two mirrors will be :

A
$$90^o$$

B
$$45^o$$

C
$$75^o$$

D
$$60^o$$

Solution

Assuming angles between two mirrors be $$\theta$$ as per geometry,
sum of angles of $$\Delta$$
$$\lambda1+\lambda2=360-20=180+\theta$$
$$3 \theta = 180^o$$
$$\theta = 60^o$$
Question 3
1 / -0

Amount of light entering in the eye is controlled by:

A
Pupil

B
Iris

C
Cornea

D
Eye lens

Solution

Hint:
It is the body’s natural reflex to regulate the amount of light entering the eye.

Explanation for correct option:

The pupil is a hole in the iris, into which the light from the surroundings enters our eyes. When a lot of light is coming from the surroundings, it contracts to restrict the amount of light that enters our eyes. When it is too dark, the pupil becomes larges to let in a large amount of light to get a better vision in the dark.

So, the amount of light entering the eye is controlled by the pupil.
Question 4
1 / -0

What is the phenomenon of light coming back after hitting a smooth plane surface called?

A
Reflection

B
Refraction

C
Dispersion

D
Splitting

Solution

Reflection.
Reflection is when light bounces off an object. If the surface is smooth and shiny, like glass, water, or polished metal, the light will reflect at the same angle as it hit the surface. This is called reflection.
Question 5
1 / -0

When the light is very bright, then:

A
Iris makes pupil expand

B
Iris makes pupil contract

C
Iris and pupil remain as they are

D
None of these

Solution

When the light is very bright, then iris makes the pupil contract so that less amount of light enters into the eye and protects it from damage.
Question 6
1 / -0

Image of our face in a plane mirror is :

A
Real

B
Magnified

C
Diminished

D
None of these

Solution

Image of our face in a plane mirror is virtual and of the same size as our face.
Question 7
1 / -0

The angle of incidence is given by the angle :

A
PON

B
QOB

C
NOQ

D
AOP

Solution

Angle of incidence is measured as the angle between the incidence ray and the normal. hence the angle of incidence is given by the angle PON.
Option A
Question 8
1 / -0

Image on the retina remains for:

A
20 s

B
10 s

C
$$\dfrac {1}{100}s$$

D
$$\dfrac {1}{16}s$$

Solution

Image on the retina remains for $$\dfrac{1}{16} \ sec$$, thus option $$D$$ is correct.
Question 9
1 / -0

Name the part of the eye which gives colour to the eyes.

A
Retina

B
Iris

C
Cornea

D
Fovea

Solution

The iris is the area of the eye that contains the pigment which gives the eye its colour.
Question 10
1 / -0

When light is incident on a polished surface ........ reflection takes place.

A
diffused

B
regular

C
irregular

D
all

Solution

In regular reflection, parallel beams are incident on a polished surface, and gets reflected as parallel beams in some other direction.

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Re-Attempt Weekly Quiz Competition

Light Test - 10

Result

Light Test - 10

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SHARING IS CARING

Question 1

$$60^{\mathrm{o}}$$

$$90^{\mathrm{o}}$$

$$120^{\mathrm{o}}$$

$$30^{\mathrm{o}}$$

Solution

Question 2

$$90^o$$

$$45^o$$

$$75^o$$

$$60^o$$

Solution

Question 3

Pupil

Iris

Cornea

Eye lens

Solution

Question 4

Reflection

Refraction

Dispersion

Splitting

Solution

Question 5

Iris makes pupil expand

Iris makes pupil contract

Iris and pupil remain as they are

None of these

Solution

Question 6

Real

Magnified

Diminished

None of these

Solution

Question 7

PON

QOB

NOQ

AOP

Solution

Question 8

20 s

10 s

$$\dfrac {1}{100}s$$

$$\dfrac {1}{16}s$$

Solution

Question 9

Retina

Iris

Cornea

Fovea

Solution

Question 10

diffused

regular

irregular

all

Solution

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