In producing a pure spectrum, the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens because a narrow slit(a) produces less diffraction(b) increases intensity(c) allows only one colour at a time(d) allows a more parallel beam when it passes through the lens.

In producing a pure spectrum, the incident light is passed through a n

1.	In producing a pure spectrum, the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens because a narrow slit(a) produces less diffraction(b) increases intensity(c) allows only one colour at a time(d) allows a more parallel beam when it passes through the lens.
Answer» (d) allows a more parallel beam when it passes through the lens.