Between the primary and secondary rainbows, there is a dark band known as Alexander’s dark band. This is because (a) Light scattered into this region interfere destructively (b) There is no light scatter into this region (c) Light is absorbed in this region (d) Angle made at the eye by the scattered rays with respect to the incident light of the sum lies between approximately $42^\circ $ and $50^\circ $
Hint: Alexander's band or Alexander's dark band is a physical phenomenon related to rainbows that were named Alexander of Aphrodisias who 1st represented it in two hundred AD. It happens because of the deviation angles of the first and secondary rainbows.
Complete step-by-step solution: Alexander's dark band lies between the first and secondary rainbow. This forms because the light scattered into this region interferes destructively. as a result of the first and secondary rainbows delimit angles ($41^\circ $ to $42^\circ$) and ($51^\circ $ to $54^\circ $ ) respectively at the observer's eye with relation to incident ray, that the scattered rays with relation to the incident ray of the sun lie between about $42^\circ $ and $50^\circ $. Option (d) is the correct answer.
Additional information: The sky within a primary rainbow is brighter than the sky outside of the bow. This is often as a result of every raindrop may be a sphere and it scatters light over a complete circular disc within the sky. The radius of the disc depends on the wavelength of the ray, with red light being scattered over a bigger angle than blue light.
Note: The sky between the primary and secondary rainbow is darker because Light rays undergoing one reflection in raindrops kind the first rainbow or brighten the sky within it. Rays reflected double are deviated to create the secondary bow or brighten the sky outside. Raindrops on lines of sight between the 2 bows cannot send light to your eye so the sky is darker there.