Wavelength of UVB is :
Ans. B. 280-320 nmThe wavelength found most effective in treating skin disease with phototherapy is UVB with warden gfh of 311 (+- 2nm) (narrow band UVB, NBUVB).The wavelengths between 4(N and 7AO nm are visible to the human eye.
250-280 nm
280-320 nm
320-400 nm
400-700 nm