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# Physics Test 6 - Modern Physics

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## 25 Questions MCQ Test JEE Main & Advanced Mock Test Series | Physics Test 6 - Modern Physics

Physics Test 6 - Modern Physics for JEE 2022 is part of JEE Main & Advanced Mock Test Series preparation. The Physics Test 6 - Modern Physics questions and answers have been prepared according to the JEE exam syllabus.The Physics Test 6 - Modern Physics MCQs are made for JEE 2022 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Physics Test 6 - Modern Physics below.
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Physics Test 6 - Modern Physics - Question 1

### An electromagnetic waves going through vacuum is described by, Then

Detailed Solution for Physics Test 6 - Modern Physics - Question 1

The relation between E0 and B0 is given by E0/B0 = c ..(1)
Here, c = speed of the electromagnetic wave
The relation between ω (the angular frequency) and k (wave number):

Therefore, from (1) and (2), we get:

Physics Test 6 - Modern Physics - Question 2

### Because of the space charge in a diode valve

Detailed Solution for Physics Test 6 - Modern Physics - Question 2 Electrons from the cathode surface of the diode valve are emitted into this negative field and their velocities will vary with different electrons. The negative field around the cathode causes the electrons to slow as they are repelled by the negative charge. the space charge in a diode valve the plate current decreases
Physics Test 6 - Modern Physics - Question 3

### A point source of light is used in a photoelectric effect. If the source is removed farther from the emitting metal, the stopping potential

Detailed Solution for Physics Test 6 - Modern Physics - Question 3

As source is moved away, intensity decreases but frequency remains same.
∴ No effect on the stopping potential.

Physics Test 6 - Modern Physics - Question 4

Moseley’s law for characteristic X-ray is  =a(z-b).In this

Physics Test 6 - Modern Physics - Question 5
The X-ray beam coming from an X-ray tube
Physics Test 6 - Modern Physics - Question 6

Cutoff wavelength of X-rays coming from a Coolidge tube depends on the

Detailed Solution for Physics Test 6 - Modern Physics - Question 6

Cutoff wavelength (λmin) is given by

λmin = hceV

Here,

h = Planck's constant

c = Speed of light

V = Accelerating voltage

e = Charge of electron

Clearly, a cutoff wavelength depends on accelerating voltage. It does not depend on the target material, separation between the target and the temperature of the filament.

Physics Test 6 - Modern Physics - Question 7

Two identical capacitors A and B are charged to the same potential V and are connected in two circuits at t = 0 as shown in figure. The charges on the

capacitors at a time = CR are, respectively

Physics Test 6 - Modern Physics - Question 8
In a transistor
Physics Test 6 - Modern Physics - Question 9

A semiconducting device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be

Physics Test 6 - Modern Physics - Question 10

In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following particles is emitted in the decay ?

Physics Test 6 - Modern Physics - Question 11

Ten grams of kept in an open containg beta-decays with a half-life of 270 days. The weigth of the material inside the container after 540 days will be very nearly

Detailed Solution for Physics Test 6 - Modern Physics - Question 11

57Co is undergoing beta decay, i.e. electron is being produced. But an electron has very less mass (9.11 x10^-31 kg) as compared to the Co atom. Therefore, after 570 days, even though the atoms undergo large beta decay, the weight of the material in the container will be nearly 10 g.

Physics Test 6 - Modern Physics - Question 12

A free neutron decays to a proton but a free proton does not decay to a neutron. This is because

Physics Test 6 - Modern Physics - Question 13

If elements with principle quantum number n>4 were not allowed in nature, the number of possible elements would be

Detailed Solution for Physics Test 6 - Modern Physics - Question 13

N=1 present K-shell and the number of elements having K shell=2 N=2 present L shell and the number of element having L shell=8 N=3 present N shell and the number of elements having N shell = 18 N=4 present N shell and the number of elements having N shell = 32 Total number = 2+8+18+32=60

Physics Test 6 - Modern Physics - Question 14

Consider the spectral line resulting from the transition n = in the atoms and ions given below. The shortest wave length is produced by

Detailed Solution for Physics Test 6 - Modern Physics - Question 14

Physics Test 6 - Modern Physics - Question 15
The equation represents
Physics Test 6 - Modern Physics - Question 16

The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature

Physics Test 6 - Modern Physics - Question 17

The X-ray emission line of tungsten occurs at   The energy difference between K and L levels in this atom is about

Physics Test 6 - Modern Physics - Question 18

The electrical conductivity of a semiconductor increases.
when em radiation of wavelength shorter than 2480 nm is incident on it. The band gap (in eV) for the semiconductor is

Physics Test 6 - Modern Physics - Question 19

The circuit shown in the figure contains tow diodes each with a forward resistance of 50 ohms and with infinite backward resistance. If the battery voltage is 6V, the current through the 100 ohm resistance (in Amperes) is

Physics Test 6 - Modern Physics - Question 20

Which of the following statement is not ture ?

*Answer can only contain numeric values
Physics Test 6 - Modern Physics - Question 21

In P.E.E, Kmax of electrons is 2.0 eV. If frequency of light is decreased by 20% then Kmax is 1.0 eV. Work function of electron emitter is (in eV) :-

Detailed Solution for Physics Test 6 - Modern Physics - Question 21

2.0 = hν - ϕ  ...... (1)
1.0 = 0.8hν - ϕ  ...... (2)
on solving we have, ϕ = 3 eV

*Answer can only contain numeric values
Physics Test 6 - Modern Physics - Question 22

When a photosensitive surface is illuminated with light of wavelength λ, the stopping potential is V. When the same surface is illuminated by light of wavelength 2λ, stopping potential is V/4. The threshold wavelength for the surface is nλ, n = ?

Detailed Solution for Physics Test 6 - Modern Physics - Question 22

*Answer can only contain numeric values
Physics Test 6 - Modern Physics - Question 23

The number of possible natural oscillations of air column in a pipe closed at one end of length 85 cm whose frequencies lie below 1250 Hz are: (velocity of sound = 340 ms–1)

Detailed Solution for Physics Test 6 - Modern Physics - Question 23

Frequency COP, nN = (2N + 1) v/4L
for N = 0,    n0 = 100 Hz
n = 1,          n1 = 300 Hz
n = 2,          n2 = 500 Hz
n = 3,          n3 = 700 Hz
n = 4,          n4 = 900 Hz
n = 5,          n5 = 1100 Hz
Total = 6
Which are less than 1250 Hz.

*Answer can only contain numeric values
Physics Test 6 - Modern Physics - Question 24

A radar has a power of 1 kW and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. What is the maximum distance upto which it can detect object located on the surface of the earth?
(Radius of earth = 6.4 × 106m)

Detailed Solution for Physics Test 6 - Modern Physics - Question 24

As We know that, Maximum distance on earth where object can be detected is d then
(h + r)2 = d2 + R2
d2 = h2 + 2Rh
Since, h < < R
So, d2 = 2Rh

d = 80 × 103m = 80 km

*Answer can only contain numeric values
Physics Test 6 - Modern Physics - Question 25

A Zener diode connected across a source voltage of 12V such that 6V drops across it. The power drawn by zener diode is 2.4 MW, Then what is the maximum value of series resistance connected in the circuit?

Detailed Solution for Physics Test 6 - Modern Physics - Question 25

VS = 12 Volt
Vdrop = 6 Volt
So, remaining voltage V = VS – Vdrop = 12 – 6
= 6 Volt
Power drawn by Zener diode P = 2.4 MW
As we know that

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