2.DVD players use red lasers with a wavelength of 650 nm, while Blu-ray players use blue lasers (hence the name) with a wavelength of 405 nm.
1. Which color would need a larger double slit spacing d to produce an interference pattern that has the first maxima 1 mm from the central bright spot?

Blue light

Explanation:

For maxima interference we have the relation

where

m =  order

d = Slit gap

we have the relation

y = First maxima =  1 mm (fixed)

D = Distance to screen = 1 m (fixed)

So, the wavelength needed should be larger.

Hence, the blue light which has higher wavelength of 650 nm is to be used as it requires larger double slit spacing.

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.