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Question
In biprism experiment, the distance of 20th bright band from the central bright band is 1.2 cm. Without changing the experimental set-up, the distance of 30th bright band from the central bright band will be ______.
Options
0.6 cm
0.8 cm
1.2 cm
1.8 cm
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Solution
In biprism experiment, the distance of 20th bright band from the central bright band is 1.2 cm. Without changing the experimental set-up, the distance of 30 bright band from the central bright band will be 1.8 cm.
Explanation:
Given:
X20 = 1.2 cm, X30 = ?
For nth bright band `x_n = (Dnlambda)/d`
For 20th bright band `x_20 = 20(Dnlambda)/d` ...(1)
For 30th bright band `x_30 = 30(Dnlambda)/d` ...(2)
Dividing equation (2) by equation (1)
`x_30/x_20 = 30/20`
∴ `x_30 = x_20 xx 3/2`
= `1.2 xx 3/2`
= 1.8 cm
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