How long does take for a freely falling object to reach 4.0 m/s

Tungsten-filament lightbulb emits light based on the temperature of the filament. which phenomenon does this demonstrate?

What is the role of the ocular lens?

Starting with only the balmer series light (visible light), how could we ensure that the solar panels generate a current that mark can use for his power station? a)by gradually increasing the brightness (amount) of light that we shine on it. b)by gradually increasing the frequency of the light we shine on it. c)by gradually increasing the wavelength of the light that we shine on it.