Electromagnetic Waves Chapter-Wise Test 7

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What property of visible light explains its role in photosynthesis?

Visible light has wavelengths that correspond to the energy levels needed to excite chlorophyll molecules in plants, driving the photochemical reactions of photosynthesis.

High frequency
Thermal energy
Suitable energy levels
Penetration depth
3

In the context of electromagnetic waves, why do oscillating charges act as effective sources?

Oscillating charges undergo acceleration, producing time-varying electric fields that induce magnetic fields, which sustain each other to form propagating electromagnetic waves.

They produce time-varying fields
They remain stationary
They eliminate magnetic fields
They propagate static fields
1

Why are infrared waves often associated with thermal imaging?

Infrared waves are emitted by objects based on their temperature, and detectors can sense these emissions to map temperature variations, making them ideal for thermal imaging.

High frequency
Visible spectrum
Temperature-dependent emission
Penetrating power
3

What is a common method to detect radio waves according to the document?

The document lists receiver's aerials as a common method to detect radio waves.

Photocells
Thermopiles
Receiver's aerials
Geiger tubes
3

What enables electromagnetic waves to propagate without a material medium?

The document states that electromagnetic waves are self-sustaining oscillations of electric and magnetic fields, requiring no material medium for propagation.

Presence of charged particles
High frequency of oscillation
Constant wavelength
Self-sustaining oscillations of fields
4

A parallel plate capacitor has a time-varying charge such that \( \frac{dQ}{dt} = 1.2 \, \text{A} \). What is the displacement current between the plates?

In a capacitor, the displacement current \( i_d \) equals the conduction current in the connecting wires, so \( i_d = \frac{dQ}{dt} = 1.2 \, \text{A} \).

1.2 A
0.6 A
2.4 A
3.6 A
1

What conclusion did Maxwell reach when the speed of electromagnetic waves matched the speed of light?

The document mentions that Maxwell concluded that light is an electromagnetic wave, as their speeds were nearly identical (\( 3 \times 10^8 \, \text{m/s} \)).

Light is an electromagnetic wave
Light travels slower than EM waves
Light requires a medium to propagate
Light has no relation to EM waves
1

Radio waves are detected using which of the following?

As per the document, radio waves are detected using receiver's aerials.

Photocells
Thermopiles
Receiver's aerials
Bolometers
3

An electromagnetic wave in vacuum has a wavelength of \( 8 \, \text{m} \). What is its frequency? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Using \( v \lambda = c \), we have \( v = \frac{c}{\lambda} = \frac{3 \times 10^8}{8} = 3.75 \times 10^7 \, \text{Hz} \).

\( 2.5 \times 10^7 \, \text{Hz} \)
\( 3 \times 10^7 \, \text{Hz} \)
\( 3.75 \times 10^7 \, \text{Hz} \)
\( 4.5 \times 10^7 \, \text{Hz} \)
3

What is the typical wavelength range of microwaves according to the document?

The document mentions that microwaves have wavelengths from \( 0.1 \, \text{m} \) to \( 1 \, \text{mm} \).

\( > 0.1 \, \text{m} \)
\( 0.1 \, \text{m} \) to \( 1 \, \text{mm} \)
\( 1 \, \text{mm} \) to \( 700 \, \text{nm} \)
\( 400 \, \text{nm} \) to \( 0.6 \, \text{nm} \)
2

Performance Summary

Score:

Category Details
Total Attempts:
Total Skipped:
Total Wrong Answers:
Total Correct Answers:
Time Taken:
Average Time Taken per Question:
Accuracy:
0