NCERT Physics Class 12 Exemplar Ch 8 Electromagnetic Waves Part 2

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Short Answer

Q 21 Show that the magnetic field B at a point in between the plates of a parallel-plate capacitor during charging is (symbols having usual meaning).


Magnetic field in parallel-plate capacitor

Magnetic Field in Parallel-Plate Capacitor

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Q 22 Electromagnetic waves with wavelength

(i) is used in satellite communication.

(ii) is used to kill germs in water purifies.

(iii) is used to detect leakage of oil in underground pipelines.

(iv) is used to improve visibility in runways during fog and mist conditions.

(a) Identify and name the part of electromagnetic spectrum to which these radiations belong.

(b) Arrange these wavelengths in ascending order of their magnitude.

(c) Write one more application of each.



  • Microwave – Radar

  • UV - LASIK eye surgery

  • X-ray - Bone fracture identification (bone scanning)

  • Infrared - Optical communication.

Q 23 Show that average value of radiant flux density ‘S’ over a single period ‘T’ is given by .