Wave Optics Test

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Wave Optics Test - 20

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Question 1
1 / -0

The inability of a lens to bring all the rays coming from a point object to focus at one single point is called

A
Spherical aberration

B
Parallex

C
Optical illusion

D
none

Solution

(A) Spherical aberration.
Question 2
1 / -0

Light is a form of _______ that we can detect with our ________ .

A
energy, ears

B
corpuscles, eyes

C
energy, eyes

D
sensation, skin

Solution

Light is a form of energy that we can detect with our eyes
Question 3
1 / -0

In an astronomical microscope, the focal length of the objective is made :

A
shorter than that of the eye piece

B
greater than that of the eye piece

C
half of the eye piece

D
equal to that of the eye piece

Solution

In an Astronomical telescope, the objective lens has a greater radius than the eyepiece.
Thus the objective lens has a greater focal length than the eyepiece.

Option B is correct.
Question 4
1 / -0

Assertion: Thin films such a soap bubble or a thin layer of oil on water show beautiful colours when illuminated by white light.
Reason: It happens due to the interference of light reflected from the upper surface of the thin film.

A
If both assertion and reason are true but the reason is the correct explanation of assertion

B
If both assertion and reason are true but the reason is not the correct explanation ofassertion

C
If assertion is true but reason is false

D
If both the assertion and reason are false

E
If reason is true but assertion is false

Solution

C
When white light is incident on thin film, the film appears coloured. These colours are due to the interference between light waves reflected from the top and bottom surfaces of thin films. The colour depends on the thickness of the film and also the angle of incidence of the light.
Question 5
1 / -0

The path difference produced by two waves is $$3.75\mu m$$ and the wavelength is $$5000 \mathring { A } $$. The point is

A
Uncertain

B
Dark

C
Partially bright

D
Bright

Solution

Interference of light is redistribution of light energy on account of superposition of light waves from two coherent sources. Interference at a point is constructive, when path difference between light waves is zero or an integral multiple of whole wavelength and interference is destructive when path difference between light waves is an odd integral multiple of half the wavelength.
Here, path $$\Delta x=3.75\mu m=3.75\times { 10 }^{ -6 }m$$
Wavelength $$\lambda =5000\mathring { A } =5\times { 10 }^{ -7 }m$$
$$\dfrac { \Delta x }{ \lambda } =\dfrac { 3.75\times { 10 }^{ -6 } }{ 5\times { 10 }^{ -7 } } =\dfrac { 37.5 }{ 5 } =7.5$$
$$\therefore \Delta x=7.5\lambda $$
Here, $$\Delta x$$ is odd multiple of $$\lambda $$, so point is dark.
Question 6
1 / -0

If the apertature of a telescope is decreased the resolving power will

A
increases

B
decreases

C
remain same

D
zero

Solution

Resolving power of a telescope=$$\dfrac{a}{1.22\lambda}$$
where $$a$$ is the aperture of the telescope.
Thus resolving power$$\propto $$ aperture.
Hence, if the aperture of telescope decreases, the resolving power decreases.
Question 7
1 / -0

The wave theory of light, in its original form, was first postulated by.

A
Isaac Newton

B
Christian Huygens

C
Thomas Young

D
Augustin Jean Fresnel

Solution

B
In 1678, Dutch physicist, Christian Huygens, believed that the light was made up of waves vibrating up and down perpendicular to the direction of the light travels and therefore formulated away of visualising wave propagation. This becomes know as Huygens principle. Huygens theory was the successful theory of light in three dimensions. Huygens suggested that the light wave peaks form from surfaces like the layers of onion. In a vacuum or other uniform mediums the light waves are spherical and these wave surfaces advance or spread out as they travel at the speed if light. This theory explains why light shining through a pinhole or slitwall spread out rather than going in straight lines.
Question 8
1 / -0

Light travels in a ________ path

A
rectilinear

B
zig zag

C
circular

D
helical

Solution

Light travels in straight line unless it passes through a change in medium.
Question 9
1 / -0

A light wave is incident normally over a slit of width $$24\times {10}^{-5}cm$$. The angular position of second dark fringe from the central maxima is $${30}^{o}$$. What is wavelength of light?

A
$$6000\mathring { A } $$

B
$$5000\mathring { A } $$

C
$$3000\mathring { A } $$

D
$$1500\mathring { A } $$

Solution

For second dark fringe,

$$d\sin{\theta}=2\lambda$$

$$\Rightarrow$$ $$24\times {10}^{-5}\times {10}^{-2}\times \sin{{30}^{o}}=2\lambda$$

$$\Rightarrow$$ $$\lambda=6\times {10}^{-7}m$$ $$=6000\mathring { A } $$
Question 10
1 / -0

Wavefront of a wave has direction with wave motion

A
parallel

B
perpendicular

C
opposite

D
at an angle of $$\theta$$

Solution

Direction of wave is perpendicular to the wavefront

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Re-Attempt Weekly Quiz Competition

Wave Optics Test - 20

Result

Wave Optics Test - 20

Score

-

Rank

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SHARING IS CARING

Question 1

Spherical aberration

Parallex

Optical illusion

none

Solution

Question 2

energy, ears

corpuscles, eyes

energy, eyes

sensation, skin

Solution

Question 3

shorter than that of the eye piece

greater than that of the eye piece

half of the eye piece

equal to that of the eye piece

Solution

Question 4

If both assertion and reason are true but the reason is the correct explanation of assertion

If both assertion and reason are true but the reason is not the correct explanation ofassertion

If assertion is true but reason is false

If both the assertion and reason are false

If reason is true but assertion is false

Solution

Question 5

Uncertain

Dark

Partially bright

Bright

Solution

Question 6

increases

decreases

remain same

zero

Solution

Question 7

Isaac Newton

Christian Huygens

Thomas Young

Augustin Jean Fresnel

Solution

Question 8

rectilinear

zig zag

circular

helical

Solution

Question 9

$$6000\mathring { A } $$

$$5000\mathring { A } $$

$$3000\mathring { A } $$

$$1500\mathring { A } $$

Solution

Question 10

parallel

perpendicular

opposite

at an angle of $$\theta$$

Solution

User

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