NEET Electromagnetic Waves — Set 11

Question 1

An electromagnetic wave has a wave number $ k = 2 \, \text{rad/m} $. What is its wavelength in vacuum?

Accepted Answer

The wave number $ k = \frac{2 \pi}{\lambda} $. Given $ k = 2 \, \text{rad/m} $, we have $ \lambda = \frac{2 \pi}{k} = \frac{2 \pi}{2} = \pi \approx 3.14 \, \text{m} $.

Question 2

Why do infrared lamps find application in physical therapy?

Accepted Answer

The document mentions that infrared waves are absorbed by materials, increasing thermal motion and heating the surroundings, which is useful for physical therapy.

Question 3

Why do infrared waves contribute to the greenhouse effect on Earth?

Accepted Answer

Infrared waves emitted by the Earth's surface are absorbed and trapped by greenhouse gases, leading to an increase in atmospheric temperature, a phenomenon known as the greenhouse effect.

NEET Physics: Electromagnetic Waves — Practice Set 11

Q1. An electromagnetic wave has a wave number \( k = 2 \, \text{rad/m} \). What is its wavelength in vacuum?

Q2. Why do infrared lamps find application in physical therapy?

Q3. Why do infrared waves contribute to the greenhouse effect on Earth?

Q4. Which of the following is true about the displacement current in a charging capacitor?

Q5. In electromagnetic wave theory, what ensures the symmetry between electric and magnetic fields in wave propagation?

Q6. An electromagnetic wave in vacuum has a frequency of \( 15 \, \text{MHz} \). What is its wavelength? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Q7. A radio tunes to stations in the \( 7.5 \, \text{MHz} \) to \( 12 \, \text{MHz} \) band. What is the corresponding wavelength range? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Q8. Why can’t one get tanned through ordinary glass windows?

Q9. What physical property of electromagnetic waves explains why they can propagate through interstellar space?

Q10. Which of the following is a common method to detect ultraviolet rays?