Dois carros, a e b, móveis se em uma estrada retilínea com volocidade constante, vª =20m/s e v=18 m/s , respectivamente. O carro A ,está, inicialmente, 500m atrás do carro B . Quanto tempo o carro A levará para alcançar o carro B?

What is the frequency of a light wave with a wavelength of 620nm

One day, after pulling down your window shade, you notice that sunlight is passing through a pinhole in the shade and making a small patch of light on the far wall. you see that the patch of light seems to be a circular diffraction pattern. it appears that the central maximum is about 1 cm across and you estimate that the distance from the window shade to the wall is about 3 m. what is (a) the average wavelength of sunlight? (b) the diameter of the pinhole?

What type of light does this light bulb produce most (i.e. at what wavelength does the spectrum have maximum intensity)?