Ray Optics and Optical Test

Result

Ray Optics and Optical Test - 23

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Weekly Quiz Competition

Question 1
1 / -0

A ray of light falls on the surface of a spherical glass paperweight making an angle $$a$$ with the normal and is refracted in the medium at angle $$b$$. The angle of deviation of the emergent ray from the direction of incident ray is :

A
$$a-b$$

B
$$2(a-b)$$

C
$$\dfrac{(a-b)}{2}$$

D
$$b-a$$

Solution

From the above figure we can see that $$\theta =2(a-b)$$

Exterior angle=sum of interior opposite angles. So answer is option B.

Question 2

1 / -0

A bubble in glass slab $$(\mu = 1.5)$$ when viewed from one side appears at $$5 \ cm$$ and $$2 \ cm$$ from other side, then thickness of slab is :

$$3.75 \ cm$$

$$3 \ cm$$

$$10.5 \ cm$$

$$2.5 \ cm$$

Solution

Acco. To given information. [ #] i use this for refractive index we know, 
refractive index = real depth/ apparent depth case 
1. x/5=1.5 
and case 2 x/2= 1.5 
now add both case we get 
x = 10.5 
as answer

Question 3
1 / -0

A thin prism of angle $$15^{o}$$ made of glass of refractive index $$\mu _{1} = 1.5$$ is combined with another prism of glass of refractive index $$\mu _{2} = 1.75$$. The combination of the prism produced dispersion without deviation. The angle of the second prism should be :

A
$$5^{o}$$

B
$$7^{o}$$

C
$$10^{o}$$

D
$$12^{o}$$

Solution

For without deviation

$$\frac{A}{A'}=-\frac{\mu ' -1}{\mu -1}$$

$$\frac{15^{o}}{A'}=-\frac{1.75-1}{1.50-1}$$

$$\frac{15^{o}}{A'}=-\frac{0.75}{0.50}$$

$$A'=-10^{o}$$
Question 4
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The angle at which the ray is incident on the second mirror is___?

A
$$10^{\circ}$$

B
$$20^{\circ}$$

C
$$30^{\circ}$$

D
$$40^{\circ}$$

Solution

$$\theta =40^{\circ}$$
$$\phi = 180 - 60 40$$
$$=80^{\circ}$$
$$\therefore i =90^{\circ}-80^{\circ}$$
$$=10$$
Question 5
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The imaginary line passing through the pole and the center of curvature of the curved mirror is called its _______.

A
Focal length

B
Radius of curvature

C
Principal axis

D
None

Solution

The imaginary line passing through the pole and the center of curvature of the curved mirror is called its principal axis.
Question 6
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The point of intersection of emergent rays is :

A
2 cm left of o.

B
2 cm right of o.

C
1 cm left of o.

D
1 cm right of o.

Solution

The point of intersection will be equal to the apparent shift caused in the image of the object.
$$ \delta s = t(1 - \dfrac{1}{\mu}) $$
= $$ 3(1 - \dfrac{1}{3}) $$
= $$2cm$$
Question 7
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Why is the colour of the clear sky blue?

A
Blue colour gets scattered the maximum.

B
water of sea is blue.

C
Blue colour gets scattered the minimum.

D
none of these.

Solution

Hint: Use the concept of scattering

Explanation:
Gases and particles in Earth's atmosphere scatter sunlight in all directions. Blue light is scattered more than other colours because it travels as shorter, smaller waves. And due to this we see the sky as blue.
Question 8
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How can we explain the reddish appearance of sun at sunrise or sunset?

A
Scattering of blue light is more than the scattering of red light

B
Scattering of red light is more than the scattering of blue light

C
Intensity of sun reduces during sunrise and sunset

D
Due to the view angle, it appears blue

Solution

During sunrise or sunset, the light has to pass through greater distance in the atmosphere. The blue light is removed as it gets scattered the most while the red colour is less scattered and reaches the observer. Thus, we find reddish colour of the sun during sunrise or sunset.
Question 9
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Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?

A
Dispersion of light

B
Scattering of light

C
Total internal reflection of light

D
Reflection of light from the earth

Solution

We see red colour of the sun at sunrise or sunset as the sun at horizon and light rays need to travel a greater distance. In the process of scattering, violet, blue and green rays in the original sunlight are removed and the transmitted beam has yellow and red dominant.
Question 10
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Beams of light are incident through the holes A and B and emerge out of the box through the holes C and D respectively as shown in the Figure. Which of the following could be inside the box?

A
a rectangular glass slab

B
a convex lens

C
a concave lens

D
a glass prism

Solution

Since lateral displacement is taking place in the parallel rays, a rectangular glass slab could be inside the box. Lateral displacement is the distance by which the incident light has been displaced after bending through the glass slab.