Mercury street lights emit light of a pale blue color with a wavelength of $436 \, nm$. Calculate its frequency.

The ejection of the photoelectron from the silver metal in the photoelectric effect experiment can be stopped by applying a stopping potential of $0.35 \ V$ when radiation of $256.7 \ nm$ is used. Calculate the work function for silver metal.

Which of the following travels with the speed of light?

Which of the following does not characterise $X$-rays?

Explain line spectra and its uses.

The laser in an audio compact disc uses light of wavelength $7.8 \times 10^2 \ nm$. What is the frequency of light emitted by the laser?