CBSE Class 12 Physics Electromagnetic Waves Notes Set D

 c. Name the social value associated with the phenomenon?

6. Charu’s father got her a new scooter. She was very happy to drive the scooter. One day she observed that there is a speedometer in the scooter, which gives the instantaneous speed of the scooter. Charu asked her father as to how the speedometer able to measure the speed. Her father knew nothing about the mechanism of measurement of speed. He went to the scooter agency to understand the same. The manager of scooter agency called a scooter mechanic who explained the working of speedometer. Charu’s father explained came home and explained everything to her. Charu thanked her father for taking interest in her curiosity

a)What according to you, are the values displayed by Charu’s father?

b)Explain the working of speedometer.

7. A school proposed to organize a science exhibition. Teacher assigned a project to Ravita to demonstrate the induced e,m.f due to change in magnetic flux. Ravita told her friend savita that she would be unable to complete the project as her mother is not feeling well. Savita told Ravita that she would help her to complete the project .Ravita completed her project of flying disc with the help of Savita .The magnitude flux in the experimental setup changes from

6x 10^-3 wb to 3x10^-2wb in 0.01s.Now answer the following question:

i)what values are displayed by Savita?

Ii)What is the induced e.m.f in the disc?

• Electromagnetic Wave:-The variation of electric and magnetic fields, perpendicular to each other, producing electromagnetic disturbance in space at right angles to each other, which have properties of waves and propagate through free space without any materialistic medium is called electromagnetic wave. 

• Properties of electromagnetic waves:

E M Waves are transverse in nature.

They are produced by oscillating or accelerating charged particles.

They do not require any medium for their propagation.

They obey principle of superposition.

They show polarization effect.

Electric field is only responsible for optical effects of EM waves.

The amplitude of electric & magnetic fields are related by E/B =C

In free space they travel with the speed C = 1√ε_ομ_ο

The energy of E M Wave is equally divided between electric and magnetic field vectors. EM waves also carry energy, momentum and information.

• Electromagnetic Spectrum: The orderly arrangement of electro magnetic radiation according to its frequency or wavelength is called electromagnetic spectrum. 

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