यदि समान आयाम और आवृत्ति वाली दो तरंगें अध्यारोपित होकर समान आयाम की एक परिणामी तरंग उत्पन्न करती हैं, तो तरंगों के बीच कलांतर (phase difference) कितना होगा?

In Young's double slit experiment using monochromatic light of wavelength λ, the intensity of light at a point on the screen where the path difference is λ is K units. The intensity of light at a point where the path difference is λ3 will be:

Unpolarized light of intensity I0 = 40 W/m2 is incident on a polaroid. The transmitted light then passes through a second polaroid whose pass axis is inclined at 30° to the first. Find the intensity of light emerging from the second polaroid.