Question

A mixture of violet light of wavelength 3800 A and 2 blue light of wavelength 4000 À is incident normally on an air film of 0.00029 mm thickness. The colour of the reflected light is (a) Red (b) blue (c) violet (d) green​

Answer 1

Answer:

A) Red

Explanation:

>> The light..which has the highest wave length, is deviated the least.

>> Among red, blue , violet and green..Red has the highest wave length

>> So, it deviates the least

Answer 2

Answer:

Since the values of m for the two wavelengths are different, the colors produced by the interference will be different. To determine the color produced by the mixture of the two, we need to consider the colors produced by each separately and then add them together.

Explanation:

The thickness of the air film is 0.00029 mm. The condition for constructive interference in a thin film is:

2nt = mλ

where n is the refractive index of the medium (air in this case), t is the thickness of the film, m is an integer, and λ is the wavelength of the incident light.

Let's first consider the violet light with a wavelength of 3800 Å. Using the above equation, we get:

2nt = mλ

2n(0.00029 mm) = m(3800 Å)

2n(0.000029 cm) = m(380 nm)

m = 2n(0.000029 cm)/(380 nm)

m = 1.84n

Similarly, for the blue light with a wavelength of 4000 Å, we get:

2nt = mλ

2n(0.00029 mm) = m(4000 Å)

2n(0.000029 cm) = m(400 nm)

m = 2n(0.000029 cm)/(400 nm)

m = 1.45n

Since the values of m for the two wavelengths are different, the colors produced by the interference will be different. To determine the color produced by the mixture of the two, we need to consider the colors produced by each separately and then add them together.

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