Concepts Of Physics MCQ Edition [Volume 1]
- Exam
- Concepts Of Physics MCQ Edition [Volume 1]
- Subject
- Physics
- Chapter
- Dispersion and Spectra
Concepts Of Physics MCQ Edition [Volume 1] · Physics · Dispersion and Spectra
To produce a pure spectrum, the incident light is passed through a...
To produce a pure spectrum, the incident light is passed through a narrow slit positioned in the focal plane of an achromatic lens because a narrow slit
Options
- Apermits only one colour at a time
- Ballows for a more parallel beam upon passing through the lens
- Cproduces less diffraction
- Dincreases the intensity
Correct answer
B. allows for a more parallel beam upon passing through the lens
Step-by-step solution
A pure spectrum is obtained when there is no overlapping of different colours.
If a wide slit is used, it acts as a collection of multiple narrow slits placed side by side. Each narrow slit produces its own spectrum, and these spectra overlap, resulting in an impure spectrum.
By using a narrow slit placed at the focal plane of an achromatic lens, the emergent light beam becomes highly parallel.
This parallel beam ensures that all rays of a particular wavelength are incident on the prism at the same angle, preventing overlapping of colours and producing a pure spectrum.
Therefore, a narrow slit allows for a more parallel beam upon passing through the lens.
If a wide slit is used, it acts as a collection of multiple narrow slits placed side by side. Each narrow slit produces its own spectrum, and these spectra overlap, resulting in an impure spectrum.
By using a narrow slit placed at the focal plane of an achromatic lens, the emergent light beam becomes highly parallel.
This parallel beam ensures that all rays of a particular wavelength are incident on the prism at the same angle, preventing overlapping of colours and producing a pure spectrum.
Therefore, a narrow slit allows for a more parallel beam upon passing through the lens.