Ray Optics and Optical Test

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Ray Optics and Optical Test - 42

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Weekly Quiz Competition

Question 1
1 / -0

The refractive indices of the material of a lens for violet, yellow and red colours of light are respectively $$1.66, 1.64$$ and $$1.62$$. The mean focal length of the lens is $$10 cm$$. Determine the chromatics aberration of the lens between the violet and the red colors.

A
$$0.225cm$$

B
$$0.324cm$$

C
$$0.576cm$$

D
$$0.625cm$$

Solution

Let $$\omega$$ be the dispersive power of the material of the lens. Then, the chromatic aberration between violet and red colors is given by:
$$f_R-f_V=\omega \times f_Y=(\dfrac{n_V-n_R}{n_Y-1})f_Y=(\dfrac{1.66-1.62}{1.64-1})\times 10=0.625cm$$
Question 2
1 / -0

For which of the two lenses $$L_1$$ and $$L_2$$ the chromatic aberration will be more if the dispersive power of the material of $$L_1$$ is less than that of $$L_2$$:

A
$$L_1$$

B
$$L_2$$

C
$$L_1=L_2$$

D
none of the above

Solution

Chromatic aberration of a lens is directly related to its dispersive power that is more the dispersive power, more is chromatic aberration.

Since, dispersive power of $$L_2$$ is more than $$L_1$$, chromatic aberration will be more in $$L_2$$.

Answer-(B)
Question 3
1 / -0

The unit of the longitudinal chromatic aberration for a thin lens is:

A
$$metre$$

B
$$gram$$

C
$$candela$$

D
$$metre^2$$

Solution

The unit of the longitudinal chromatic aberration for a thin lens is metre because there is a measurement of distance or length.
Question 4
1 / -0

The chromatic aberration due to a lens depends upon:

A
focal length of the lens.

B
dispersive power of the material of the lens.

C
both A and B.

D
none of the above.

Solution

The chromatic aberration due to a lens depends upon focal length of the lens and dispersive power of the material of the lens.

Because Chromatic aberration is caused by the different colors, and hence wavelengths of light having different refractive indices. This means that if white light is refracted in a prism the light is split into its different wavelengths, seen as a spectrum of colors (think rainbow).
Question 5
1 / -0

The lateral shift produced by a glass slab increase with _________ in the thickness of the glass slab.

A
increase

B
decrease

C
remains the same

D
data insufficient

Solution

Lateral shift produced by a glass slab is given by
Lateral shift $$\lambda=\dfrac{t}{\cos r}(\sin(i-r))$$
Here t is the thickness of the slab which is directly proportional to lateral shift. Hence if thickness increases, lateral shift also increases.
Question 6
1 / -0

The type of lens used as a simple microscope.

A
Binocular lens

B
Plano concave lens

C
Concave convex lens

D
Convex lens

Solution

The use of a single convex lens or groups of lenses are found in simple magnification devices such as the magnifying glass and eyepieces for telescopes and microscopes.
Question 7
1 / -0

Calculate the index of refraction of a liquid from the following into glass:
Reading for the bottom of an empty breaker : 11.324 cm
Reading for the bottom of the beaker, when partially filled with the liquid : 11.802 cm
Reading for the upper level of the liquid in the beaker : 12.895 cm

A
1.437

B
2.437

C
3.437

D
4.437

Solution

Given: Reading for the bottom of an empty breaker : 11.324 cm, reading for the bottom of the beaker, when partially filled with the liquid : 11.802 cm, reading for the upper level of the liquid in the beaker : 12.895 cm
To find the refractive index of the liquid
Solution:
Real depth of the beaker = 12.895--11.324=1.571
Apparent depth = 12.895-11.802=1.093
Refractive index of the liquid = $$\dfrac {\text{Real Depth}}{\text{Apparent Depth}}=\dfrac {1.571}{1.093}=1.437$$
Question 8
1 / -0

One way to reduce chromatic aberration is by:

A
using multiple lenses

B
cutting the lens in half

C
praying to the lens to stop behaving erratically

D
all of the above

Solution

In the earliest uses of lenses, chromatic aberration was reduced by increasing the focal length of the lens where possible,so we can use multiple lenses to reduce
chromatic aberration.
Question 9
1 / -0

When an extended white object is placed before a convex lens, colored images are formed. The image of the smallest size is of the color:

A
violet

B
green

C
yellow

D
red

Solution

Since the wavelength of violet is largest. It shows less deviation and the image formed is the smallest.

The image of the smallest size of color is violet.
Question 10
1 / -0

The focal length of a convex lens made of flint glass is $$15cm$$. To remove its chromatic aberration, it is placed in contact with a concave lens made of crown glass. Find the focal length of the concave lens. The ratio of dispersive powers of flint glass to crown glass is $$1.5$$.

A
$$-10cm$$

B
$$+10cm$$

C
$$-20cm$$

D
$$+20cm$$

Solution

Given: The focal length of a convex lens made of flint glass is 15cm. To remove its chromatic aberration, it is placed in contact with a concave lens made of crown glass. The ratio of dispersive powers of flint glass to crown glass is 1.5.
To find the focal length of the concave lens
Solution:
Let focal length of the convex lens be $$f_1$$ and focal length of the concave lens be $$f_2$$ and ratio of dispersice power of the flint glass is $$\dfrac {\omega_2}{\omega_1}=1.5$$
For achromatic combination,
$$\dfrac {f_1}{f_2}=-\dfrac {\omega_2}{\omega_1}\\\implies \dfrac {15}{f_2}=-1.5\\\implies f_2=-10cm$$
Hence the focal length of the concave lens is -10cm

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Re-Attempt Weekly Quiz Competition

Ray Optics and Optical Test - 42

Result

Ray Optics and Optical Test - 42

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SHARING IS CARING

Question 1

$$0.225cm$$

$$0.324cm$$

$$0.576cm$$

$$0.625cm$$

Solution

Question 2

$$L_1$$

$$L_2$$

$$L_1=L_2$$

none of the above

Solution

Question 3

$$metre$$

$$gram$$

$$candela$$

$$metre^2$$

Solution

Question 4

focal length of the lens.

dispersive power of the material of the lens.

both A and B.

none of the above.

Solution

Question 5

increase

decrease

remains the same

data insufficient

Solution

Question 6

Binocular lens

Plano concave lens

Concave convex lens

Convex lens

Solution

Question 7

1.437

2.437

3.437

4.437

Solution

Question 8

using multiple lenses

cutting the lens in half

praying to the lens to stop behaving erratically

all of the above

Solution

Question 9

violet

green

yellow

red

Solution

Question 10

$$-10cm$$

$$+10cm$$

$$-20cm$$

$$+20cm$$

Solution

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