A single slit Fraunhofer diffraction pattern is formed with white light. For what wavelength of light the third secondary maximum in the diffraction pattern coincides with the secondary maximum in the pattern for red light of wavelength 6500 Å ?

Options

A. 4400Å
B. 4100Å
C. 4642.8Å
D. 9100Å

Answer

C

Explanation

`x=((2n+1)lamdaD)/(2a)`
For red light, `x=((4+1)D)/(2a)xx6500Å`
For other light, `x=((6+1)D)/(2a)xxlamdaÅ`
x is same for each.
`therefore5xx6500=7xxlamdarArr5/7xx6500=4642.8Å`.