Question

A room is illuminated by an extended source. The illuminance at a particular portion can be increased by

• A. moving the source
• B. rotating the source
• C. changing the colour of the source
• D. placing mirrors at proper positions
• E. all of these

Answer 1

The correct option is E all of these

A. Moving the source would change the intensity of light by doppler effect.

B Rotating the source would cause change of intensity due to doppler effect at different points of the extended source.

C. Intensity of incident wave varies with the wavelength of the light. Lower the wavelength, higher the energy.

D. Placing mirrors at proper postitions can reflect and concentrate the otherwise spread light to one single place to increase the intensity.