An unknown spectrum has a red line at 653 nm and a violet line at 450 nm. What angular separation between these two spectral lines is obtained with a diffraction grating that has 3,500 lines/cm

think its the third option

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.