Calculate the average power output (in watts) of a photodetector that collects 8.0 x 107 photons in 3.8 ms from monochromatic light of wavelength (a) 470 nm, the wavelength produced by some commercially available light-emitting diodes (led), and (b) 780 nm, a wavelength produced by lasers that are commonly used in compact disc (cd) players. hint: the total energy emitted by a source or collected by a detector in a given interval is its power multiplied by the time interval of interest (1 j = 1 w s).

For the car in the picture ,in which direction is the normal force? -into the screen -down -out of the screen -up

While carrying a heavy box up the stairs, you set the box on a step and rest. then you pick up the box and carry it to the top of the stairs. describe these actions in terms of balanced and unbalanced forces acting on the box.

1. what is the relationship between wavelength and the penetrating power of an electromagnetic wave? a) the penetrating power has no relationship to the wavelength. b) the penetrating power increases as the wavelength increases. c) the penetrating power decreases as the wavelength increases. d) the penetrating power decreases as the wavelength decreases. 2. as ice melts and turns into water, the speed of sound through the material would most likely do what? justify your answer. a) the speed would not change because the material is always water. b) the speed of sound would increase because the density of water is less than that of ice. c) the speed of sound would increase because energy is added to ice in order to make it melt. d) the speed of sound would decrease because sound travels faster through solids than liquids. 3.which of these waves need a medium to travel through? a) sound b) x-rays c) infrared rays d) visible light