Which is true about UVA and UVB rays? A. Both rays can be blocked 100% by sunscreen
B. UVA protects the surface, UVB protects beneath the surface
C. UVB rays cause burning, UVA rays cause premature aging
D. UVA rays cause burning, UVB rays cause premature aging

I need help :

What is the length x of the side of the triangle below? (hint: use the cosine function)

Astudent is performing an experiment comparing sound and light waves. the student gathers the following data. what conclusion does the student most likely make based on this data? light waves always travel the same speed; however, the speed of sound is determined by the medium that it travels through. all sound waves always have the same energy, so the temperature of the medium does not affect wave speed. light needs to vibrate particles, so it travels fastest in tightly packed solids, while sound does not need a medium, so it travels fastest in a gas. tightly packed particles in solids slow down the light waves; however, sound waves make particles bounce into each other, so they travel faster in solids.

Ablock having mass m slides down an inclined plane. the force of friction between the block and the inclined plane is f, the block's weight is m g, and the normal force is n. (a) draw a free – body force diagram showing the forces acting on the block. (b) write down all relevant newton’s equations for a given situation.