The biprism experiment is performed by using first the blue light of wavelength 4800 Å and then with red light. It is found that the fourth bright band of blue light coincides with the third bright band of red light. What is the wavelength of red light?

Options

A. 4800Å
B. 6000Å
C. 6400 Å
D. 5600Å

Answer

C

Explanation

`n_(1)=4, lambda4800^(@)m n_(2)=3m lambda_(2) ?`
for same apth difference
`n_(1)lambda_(1)=n_(2)lambda_(2)`
`:.lambda_(2)=(n_(1)lambda_(2))/(n_(2))=(4xx4800)/(3)`
`lambda_(2)=6400A^(@)`