We see black colour in absence of light. Black colour absoorbs all the light, ( just opposite of white) and hence we do not see any colour. Black colour is also related to darkness.
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Answer:
A lens
Explanation:
A lens forms images when light passes Through it bending the rays of in the process.A phenomena called refraction and the speed of light changes in the process because it enters a medium since it's wavelength is reduced.
Answer:

Explanation:
<h3><u>Given data:</u></h3>
Frequency = f = 200 Hz
Velocity = v = 400 m/s
<h3><u>Required:</u></h3>
Wavelength = λ = ?
<h3><u>Formula:</u></h3>
v = fλ
<h3><u>Solution:</u></h3>
Put the givens in the formula
400 = (200)λ
Divide 200 to both sides
400/200 = λ
2 m = λ
λ = 2 m
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