Electromagnetic Waves Test

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Electromagnetic Waves Test - 14

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Weekly Quiz Competition

Question 1
1 / -0

The propagation constant of a photon of wavelength $$6284 \ A^o$$

A
$$6284$$ meter$$^{-1}$$

B
$$10^{5} cm^{-1}$$

C
$$10^{5}$$ meter$$^{-1}$$

D
$$10^{7} cm^{-1}$$

Solution

The propagation constant can be written as
$$K= \dfrac{2 \pi}{ \lambda}=\dfrac{60284}{6284 \times 10^{-8}}= 10^{5} cm^{-1}$$
Question 2
1 / -0

The frequency of incident light falling on a photosensitive metal plate is doubled, the kinetic energy of the emitted photoelectrons is

A
Unchanged

B
Less than doubled

C
Double the earlier value

D
More than doubled

Solution

$$v \rightarrow 2v$$ $$hv-hv_o = K G_{max}$$
So, $$KG_{max} > 2 KG_{max}$$
as $$hv_o $$ is constant
Question 3
1 / -0

Choose the correct answer from the alternatives given.
Displacement current goes through the gap between the plates of a capacitor when the charge of the capacitor

A
increases

B
decreases

C
increases or decreases

D
is zero

Solution

Displacement current inside a capacitor is given by:-

$$i_d=\epsilon_0 \dfrac{\phi_E}{dt}$$

where $$\phi_E$$ is the electric flux inside the capacitor

The displacement current is developed inside a capacitor when there is a change in the electric flux linked with the capacitor. The change in electric flux can occur in both the cases either the charge increases or decreases on the capacitor. This will lead to a change in flux linked with the coil.

Thus, option $$(C)$$ is correct.

Question 4

1 / -0

In case of the electromagnetic waves the angle between the electric and magnetic field vectors is

$$\pi$$

$$\pi/2$$

zero

none of these

Solution

Electromagnetic waves are formed when an electric field couples with a magnetic field . The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave, as shown in figure

Question 5
1 / -0

Instantaneous displacement current $$1A$$ in the space between the parallel plates of $$1\mu F$$ capacitor can be established by changing the potential difference at the rate of:

A
$$0.1V/s$$

B
$$1V/s$$

C
$${10}^{6}V/s$$

D
$${10}^{-6}V/s$$

Solution

In a capacitor of capacitance $$C$$,
$$V=\dfrac{q}{C}$$
$$\implies \dfrac{dV}{dt}=\dfrac{i}{C}=\dfrac{1A}{1\mu F}=10^{6}V/s$$
Question 6
1 / -0

The displacement current was first populated by

A
Maxwell

B
Marconi

C
Ampere

D
Hertz

Solution

In electromagnetism, displacement current is a quantity appearing in Maxwell's equations that is defined in terms of the rate of change of electric displacement field.
Question 7
1 / -0

Displacement current is

A
continuous when electric field is changing in the circuit

B
continuous when magnetic field is changing in the circuit

C
continuous in both types of fields

D
continuous through wires and resistance only

Solution
Question 8
1 / -0

According to Maxwell's hypothesis, a changing electric field gives rise to

A
an electromagnetic force

B
electric displacement current

C
magnetic field

D
pressure gradient

Solution

$$Answer:-$$ C option
$$\nabla \times B={ \mu }_{ 0 }(J+{ \epsilon }_{ 0 }\dfrac { dE }{ dt } )$$
using this equation of maxwell we can say changing electric field $$\dfrac{dE}{dt}$$ induces magnetic field.
Question 9
1 / -0

Maxwell's equation describe the fundamental laws of

A
electricity

B
magnetism

C
mechanics

D
both (A) and (B)

Solution

Maxwell's equation describe the fundamental laws of electricity and magnetism. His equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents.
Question 10
1 / -0

According to Maxwell's equation, the velocity of light in any medium is expressed as

A
$$\displaystyle\frac{1}{\sqrt{\mu_0\varepsilon_o}}$$

B
$$\displaystyle\frac{1}{\sqrt{\mu\varepsilon}}$$

C
$$\displaystyle\sqrt{\frac{\mu}{\varepsilon}}$$

D
$$\displaystyle\sqrt{\frac{\mu_0}{\varepsilon}}$$

Solution

Velocity of light in a medium,

$$\displaystyle c=\frac{1}{\sqrt{\mu_0\varepsilon_o\mu_r\varepsilon_r}}=\frac{1}{\sqrt{\mu\varepsilon}}$$

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Re-Attempt Weekly Quiz Competition

Electromagnetic Waves Test - 14

Result

Electromagnetic Waves Test - 14

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SHARING IS CARING

Question 1

$$6284$$ meter$$^{-1}$$

$$10^{5} cm^{-1}$$

$$10^{5}$$ meter$$^{-1}$$

$$10^{7} cm^{-1}$$

Solution

Question 2

Unchanged

Less than doubled

Double the earlier value

More than doubled

Solution

Question 3

increases

decreases

increases or decreases

is zero

Solution

Question 4

$$\pi$$

$$\pi/2$$

zero

none of these

Solution

Question 5

$$0.1V/s$$

$$1V/s$$

$${10}^{6}V/s$$

$${10}^{-6}V/s$$

Solution

Question 6

Maxwell

Marconi

Ampere

Hertz

Solution

Question 7

continuous when electric field is changing in the circuit

continuous when magnetic field is changing in the circuit

continuous in both types of fields

continuous through wires and resistance only

Solution

Question 8

an electromagnetic force

electric displacement current

magnetic field

pressure gradient

Solution

Question 9

electricity

magnetism

mechanics

both (A) and (B)

Solution

Question 10

$$\displaystyle\frac{1}{\sqrt{\mu_0\varepsilon_o}}$$

$$\displaystyle\frac{1}{\sqrt{\mu\varepsilon}}$$

$$\displaystyle\sqrt{\frac{\mu}{\varepsilon}}$$

$$\displaystyle\sqrt{\frac{\mu_0}{\varepsilon}}$$

Solution

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