Question

The wavelength of orange light emitted by $krypton-86$ in vacuum is used as standard length because

• A. eyes are most sensitive for orange colour
• B. orange light is not easily absorbed
• C. it is unaffected by temperature, pressure etc.
• D. all the above.

Answer 1

Answer: (C)

This wavelength is defined, produced and measured accurately and is unaffected by the physical conditions.