5physics questions for 25 points don't answer if you don't know it. i'll mark the best response as 1. a is an object in space with such intense gravity that no light can escape? a- red shift b- galaxy c- black hole d- nebula 2. a galaxy is a group of billions of stars, star systems, star clusters, dust and gas bound together by a- light b- gravity c- friction d- water 3. which of the following is not a type (shape) of galaxy? a- spiral b- triangular c- elliptical d- irregular 4. what is the shape of our milky way galaxy? a- spiral b- triangular c- elliptical d- irregular 5. there are billions of galaxies in the universe. how are they classified? a- by their colors and luminosity b- by their size and shape c- by their size and color d- by their size and brightness

Antireflective coatings on solar cells are often made by applying a thin film of silicon nitride (sinx), which has an index of refractive of 1.2, on the top of the silicon solar cell, which has a refractive index of about 3.5. however, the sun emits radiation of various wavelengths which the solar cell absorbs, and the antireflective coating can only absolutely minimize the reflection of one of these wavelengths. the coating thickness is chosen to reduce the reflection of green/yellow light (e = 2.2 ev), which is the most intense color in the solar spectrum (shown below). which of the following coatings would minimize reflection of green/yellow light? the answer is 820 nm how? what is the angular width of the central maximum of an electron traveling at 2 x 108 m/s going through a single slit of width 1 mm.