# NCERT Physics Class 12 Exemplar Ch 8 Electromagnetic Waves Part 1 (For CBSE, ICSE, IAS, NET, NRA 2022)

Doorsteptutor material for CBSE/Class-12 is prepared by world's top subject experts: get questions, notes, tests, video lectures and more- for all subjects of CBSE/Class-12.

Q 14 Why is the orientation of the portable radio with respect to broadcasting station important?

Ans:

• As electromagnetic waves are plane polarized, so the receiving antenna should be parallel to electric/magnetic part of the wave.

Q 15 Why does microwave oven heats up a food item containing water molecules most efficiently?

Ans:

• Frequency of the microwave matches the resonant frequency of water molecules.

Q 16 The charge on a parallel plate capacitor varies as . The plates are very large and close together (area , separation ) . Neglecting the edge effects, find the displacement current through the capacitor?

Ans:

Q 17 A variable frequency a. c source is connected to a capacitor. How will the displacement current change with decrease in frequency?

Ans:

• On decreasing the frequency, reactance will increase which will lead to decrease in conduction current.
• In this case ; hence displacement current will decrease.

Q 18 The magnetic field of a beam emerging from a filter facing a floodlight is given by . What is the average intensity of the beam?

Ans:

Q 19 Poynting vectors S is defined as a vector whose magnitude is equal to the wave intensity and whose direction is along the direction of wave propagation. Mathematically, it is given by . Show the nature of S vs t graph.

Ans: