Answer to Question #197680 in Physics for Madillo

Question

4. A learner investigates one of the wave phenomena. He places a red filter in front of a straight 

filament lamp and observes the light through a SINGLE SLIT from a distance of 2 m.

The learner records the following observation: 

“A broad central red band and to its sides alternate dark and red bands of different widths.”

1. Explain the occurrence of red and dark bands. (2)

The learner now replaces the red filter with a blue filter and repeats the experiment. 

2.How will the broadness of the blue bands compare to that of the red bands? Write down 

BROADER THAN, NARROWER THAN or EQUAL TO. Explain the answer.

Answer 1

1. There are red and dark bands because waves of light shifted from each other a bit interfere with each other, and peaks and troughs 'cancel' each other when meet together.
2. The broadness of the blue bands will be narrower than that of red because blue has a shorter wavelength.