NEET Electromagnetic Waves — Set 17

Question 1

According to Maxwell's equations, what is the relationship between the speed of electromagnetic waves in vacuum and the constants $ \mu_0 $ and $ \varepsilon_0 $?

Accepted Answer

The document states that the speed $ c $ of electromagnetic waves in vacuum is given by $ c = \frac{1}{\sqrt{\mu_0 \varepsilon_0}} $.

Question 2

An electromagnetic wave in vacuum has a wavelength of $ 20 \, \text{m} $. What is its frequency? (Given $ c = 3 \times 10^8 \, \text{m/s} $)

Accepted Answer

Using $ v \lambda = c $, we have $ v = \frac{c}{\lambda} = \frac{3 \times 10^8}{20} = 1.5 \times 10^7 \, \text{Hz} $.

Question 3

What property of electromagnetic waves explains why their speed in a medium is less than in vacuum?

Accepted Answer

The speed in a medium is reduced due to the medium’s permittivity ($ \varepsilon $) and permeability ($ \mu $), giving $ v = \frac{1}{\sqrt{\mu \varepsilon}} $, which is less than $ c $ because $ \varepsilon > \varepsilon_0 $ and $ \mu > \mu_0 $.

NEET Physics: Electromagnetic Waves — Practice Set 17

Q1. According to Maxwell's equations, what is the relationship between the speed of electromagnetic waves in vacuum and the constants \( \mu_0 \) and \( \varepsilon_0 \)?

Q2. An electromagnetic wave in vacuum has a wavelength of \( 20 \, \text{m} \). What is its frequency? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Q3. What property of electromagnetic waves explains why their speed in a medium is less than in vacuum?

Q4. In the context of electromagnetic wave propagation, what ensures that the wave remains transverse?

Q5. Why are ultraviolet rays more effective than visible light for sterilizing surfaces?

Q6. Which of the following devices is used to detect infrared waves?

Q7. An electromagnetic wave in vacuum has a frequency of \( 25 \, \text{MHz} \). What is its wavelength? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Q8. A capacitor is charged such that the electric flux through a surface between the plates changes at a rate of \( 5 \times 10^{10} \, \text{Vm/s} \). What is the displacement current? (Given \( \varepsilon_0 = 8.85 \times 10^{-12} \, \text{F/m} \))

Q9. Which frequency range corresponds to the FM radio band as per the document?

Q10. What is the approximate wavelength range of gamma rays as per the document?