$A$ white screen illuminated by green and red light appears to be

Dark lines on the solar spectrum are due to

$A$ laser beam can be focused on an area equal to the square of its wavelength. $A$ $He-Ne$ laser radiates energy at the rate of $1 \, mW$ and its wavelength is $632.8 \, nm$. The intensity of the focused beam will be:

Light from a sodium lamp is passed through cold sodium vapours. The spectrum of the transmitted light consists of:

According to the corpuscular theory of light,which of the following phenomena can be explained?

$A$ laser beam is used for surgery because it can be...