What is the frequency of violet light having wavelength 400 nm ?

Identify the product ' B ' in the following series of reactions.

$$\text { Propan -1-ol } \xrightarrow[623 \mathrm{~K}]{\mathrm{A}_2 \mathrm{O}_3} \mathrm{~A} \xrightarrow[\text { i) } \mathrm{H}_2 \mathrm{O}]{\text { i) } \mathrm{Conch}_2 \mathrm{SO}_4} \mathrm{~B}$$

Identify an aldehyde used in margarine and in food for its buttery odour.

Identify the major product formed in the bromination of 2-Methylpropane.