Electromagnetic Waves — Previous-Year Questions

Q1. A parallel-plate capacitor with circular plates of radius R = 5 cm is charged so that E between the plates changes at dE/dt = 10¹⁰ V/m·s. The displacement current through the gap is:

Q2. In Ampère–Maxwell law, the displacement current term is necessary because:

Q3. A capacitor of 1 μF is connected to a 50 Hz AC source of peak voltage 100 V. The peak displacement current between the plates is:

Q4. Between the plates of a parallel-plate capacitor being charged, which statement is correct?

Q5. The displacement current produces:

Q1. An EM wave in vacuum has E₀ = 60 V/m. The amplitude of B₀ is:

Q2. In an EM wave, the relationship between E, B, and the propagation direction k̂ is:

Q3. Light enters glass of index 1.5 from air. Which quantity is UNCHANGED?

Q4. If the permittivity of a medium is 4ε₀ and permeability is μ₀, the speed of light in the medium is:

Q5. Which of the following is NOT a property of EM waves in vacuum?

Q6. Hertz's 1887 experiment confirmed:

Q1. The wavelength of a 100 MHz FM radio wave in vacuum is:

Q2. Which EM band lies between visible and X-rays?

Q3. A photon of wavelength 200 nm belongs to which band?

Q4. Which of the following has the SHORTEST wavelength?

Q5. Which EM band is used in night-vision goggles?

Q6. Microwave ovens operate at 2.45 GHz primarily because:

Q1. An EM wave in vacuum has E₀ = 100 V/m. The time-averaged intensity is:

Q2. A 100 W isotropic lamp radiates uniformly. Intensity at 5 m is:

Q3. If E₀ of an EM wave is doubled, the intensity becomes:

Q4. The Poynting vector at a point in an EM wave gives:

Q5. Solar intensity at Earth's orbit is 1.36 kW/m². The peak E-field of solar EM waves is:

Q1. Sunlight of intensity 1400 W/m² falls on a perfectly black absorbing surface. The radiation pressure is:

Q2. The same intensity falls on a perfect MIRROR instead of an absorber. The pressure becomes:

Q3. A 100 W lamp radiates isotropically. The radiation force on a flat absorber of area 1 m² placed 10 m away (normal incidence) is:

Q4. A solar sail (perfect reflector, area 100 m²) is in space at 1 AU. Force on it (solar constant 1361 W/m²):

Q5. Why do comet tails point AWAY from the Sun?

Q1. Yellow sodium light has λ = 589 nm in vacuum. Its frequency is:

Q2. A wave of λ = 600 nm in vacuum enters glass (n = 1.5). Its wavelength inside the glass is:

Q3. The energy of a 620 nm photon in eV is approximately:

Q4. An EM wave has period 5 × 10⁻⁹ s. Its wavelength is:

Q5. When light passes from vacuum into a medium of index n, which is true?