# KVPY (Kishore Vaigyanik Protsahan Yojana) Stream SB-SX (Class 12 & 1st Year B.Sc.) Physics: Questions 251 - 254 of 268

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## Question number: 251

Appeared in Year: 2016

MCQ▾

### Question

Electrons accelerated from rest by an electrostatic potential are collimated and sent through a Young’s double slit setup. The fringe width is . If the accelerating potential is doubled then the width is now close to –

### Choices

Choice (4) Response

a.

b.

c.

d.

## Question number: 252

Appeared in Year: 2016

MCQ▾

### Question

Photons of wavelength are incident on a metal. The most energetic electrons ejected from the metal are bent into a circular are of radius by a perpendicular magnetic field having a magnitude . The work function of the metal is –

(Where symbols have their usual meanings)

### Choices

Choice (4) Response

a.

b.

c.

d.

## Question number: 253

Appeared in Year: 2016

MCQ▾

### Question

A hearing test is conducted on an aged person. It is found that her threshold of hearing is 20 decibels at and it rises linearly with frequency to decibels at . The minimum intensity of sound that the person can hear at is –

### Choices

Choice (4) Response

a.

times than that at

b.

times than that at

c.

times than that at

d.

times than that at

## Question number: 254

Appeared in Year: 2016

MCQ▾

### Question

A monochromatic light source of wavelength is placed slightly above a plane mirror as shown. Image of in can be used as a virtual source to produce interference fringes on the screen. The distance of source from is , and the distance of screen from is (figure is not to scale). If the angle radians, the width of the interference fringes observed on the screen is –

### Choices

Choice (4) Response

a.

b.

c.

d.

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