The electron is

What is the ratio of the energy of photons having wavelengths $2000 \ \mathring{A}$ and $4000 \ \mathring{A}$?

The Vividh Bharati station of All India Radio,Delhi,broadcasts on a frequency of $1368 \, kHz$ (kilo hertz). Calculate the wavelength of the electromagnetic radiation emitted by the transmitter. Which part of the electromagnetic spectrum does it belong to?

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?

Which of the following coloured light has the highest energy?

The frequency of a light wave is $12 \times 10^{14} \ s^{-1}$. The wave number associated with it is .......