Physics Test 148

Result

Physics Test 148

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Question 1
4 / -1

A convex lens is dipped in a liquid, whose refractive index is greater than the refractive index of lens material, then convex lens will behave as

A
convex lens

B
concave lens

C
plane glass

D
None of these

Solution

A convex lens is dipped in a liquid whose refractive index is more than of lens material, then the nature of the lens changes and it behaves like a concave lens.
Question 2
4 / -1

An object is placed at the focus of convex mirror. The image will be at

A
centre of curvature

B
focus

C
infinity

D
no image will be formed

Solution

In this case, the object is placed on the right side of the mirror as the, focus of a convex mirror is on its right side, then no image will be formed.
Question 3
4 / -1

If an unpolarised light is polarised by reflection, then the angle between refracted and reflected light is

A
120°

B
60°

C
180°

D
90°

Solution

If an unpolarised light is polarised by reflection them, the angle between refracted and reflected light is 90°, i.e. the reflected and referacted rays are mutually perpendicular.
Question 4
4 / -1

In Young’s double slit experiment, the central fringe is

A
always bright

B
always dark

C
Neither bright nor dark

D
None of these

Solution

In Young’s double slit experiment, the central fringe is always bright because of constructive interference at that position.
Question 5
4 / -1

A Young’s double slit experiment uses a monochromatic source. The shape of the interference fringe formed on a screen is

A
hyperbola

B
circle

C
straight line

D
parabola

Solution

The shape of the interference fringe formed on the screen is hyperbola. If D is not very large as compared to fringe width.
Question 6
4 / -1

When intensity of incident photon increases in photoelectric experiment, then

A
kinetic energy of emitted electron increases

B
value of stopping potential increase

C
photoelectric current increases

D
All of the above

Solution

In photoelectric experiment, intensity of incident photon is directly proportional to the number of photon emitted.

So, when we increase the intensity, then number of electrons ejected per second increases, thereby increasing the photoelectric current.
Question 7
4 / -1

An electron and proton are accelerated through same potential, then the ratio of their de-Broglie waves will be (where, me and mp are mass of electron and proton, respectively)

A

B

C

D

Solution
Question 8
4 / -1

The rest mass of photon moving with velocity c having wavelength λ is

A

B

C

D
zero

Solution
Question 9
4 / -1

Photoelectric emission takes place

A
When frequency of incident radiation is greater than its threshold frequency

B
When wavelength of incident photon is less than its threshold wavelength

C
When frequency of incident radiation is equal to its threshold frequency

D
All of the above

Solution

For the photoelectric emission to take place the photons should have the energy greater than or equal to the work function of the metal, i.e.

where, h is the Planck constant, f is the frequency of the incident photon and W is the work function of the metal used.
Question 10
4 / -1

The de-Broglie wavelength for electron by accelerated 100 V potential is

A
1.23 nm

B
1.23 Å

C
1.2 nm

D
1.25 Å

Solution