Light of wavelength 587.5 nm illuminates a slit of width 0.75mm. At what distance from the slit should a screen be placed if the first minimum in the diffraction pattern is to be 0.85mm from the central maximum?

Ray tracing vs. local lighting: pros and cons?

Light passes through a slit that is about 5 × 10-³ m high and 5 × 10-7m wide. The central bright light visible on a distant screen will be (a) about 5 x 10-³m high and about 5 × 10-7 m wide. (b) about 5 x 10-³m high and wider than 5 x 10-7 m. (c) about 5 × 10-³ m high and narrower than 5 × 10-7m. (d) taller than 5 x 10-3 m high and wider than 5 x 10-7 m. (e) taller than 5 × 10-³ m high and about 5 × 10-7 m wide.

A point source emitting uniformly in all directions is placed above a table-top at a distance of 0'50 m from ic. The luminous flux of the source is 1570 lumen. Find the illuminance at a small surface area of the table-top (a) directly below the source and (b) at a distance of 0:80 m from the source.