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# Physics Test 6 - Modern Physics

## 25 Questions MCQ Test Mock Test Series for JEE Main & Advanced 2022 | Physics Test 6 - Modern Physics

Description
This mock test of Physics Test 6 - Modern Physics for JEE helps you for every JEE entrance exam. This contains 25 Multiple Choice Questions for JEE Physics Test 6 - Modern Physics (mcq) to study with solutions a complete question bank. The solved questions answers in this Physics Test 6 - Modern Physics quiz give you a good mix of easy questions and tough questions. JEE students definitely take this Physics Test 6 - Modern Physics exercise for a better result in the exam. You can find other Physics Test 6 - Modern Physics extra questions, long questions & short questions for JEE on EduRev as well by searching above.
QUESTION: 1

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

Solution:

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:

QUESTION: 2

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

Solution: 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
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

Solution:

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

QUESTION: 4

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

Solution:
QUESTION: 5
The X-ray beam coming from an X-ray tube
Solution:
QUESTION: 6

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

Solution:

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.

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

Solution:
QUESTION: 8
In a transistor
Solution:
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

Solution:
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 ?

Solution:
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

Solution:

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.

QUESTION: 12

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

Solution:
QUESTION: 13

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

Solution:

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

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

Solution:

QUESTION: 15
The equation represents
Solution:
QUESTION: 16

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

Solution:
QUESTION: 17

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

Solution:
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

Solution:
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

Solution:
QUESTION: 20

Which of the following statement is not ture ?

Solution:
*Answer can only contain numeric values
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) :-

Solution:

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

*Answer can only contain numeric values
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 = ?

Solution:

*Answer can only contain numeric values
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)

Solution:

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
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)

Solution:

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
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?

Solution:

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