The work function of a metal surface is 4.80 × 10-19 j. the maximum speed of the electrons emitted from the surface is va = 7.7 × 105 m/s when the wavelength of the light is λa. however, a maximum speed of vb = 5.1 × 105 m/s is observed when the wavelength is λb. find the wavelengths λa and λb.

Explanation:

h = Planck's constant =

c = Speed of light =

m = Mass of electron =

= Work function =

= Velocity of A particle =

= Velocity of B particle =

The wavelength is given by

The wavelength

The wavelength

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air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.