- 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
- allows only one colour at a time ,
- produces less diffraction ,
- increases intensity ,
- allows a more parallel beam when it passes through the lens
- 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
- allows only one colour at a time ,
- produces less diffraction ,
- increases intensity ,
- allows a more parallel beam when it passes through the lens