The 488 nm line from an argon ion laser is doppler broadened to 2.7×109 hz. given that the laser’s mirrors are 1 m apart, determine the number of longitudinal modes within the gain bandwidth of the 488 nm line. assume that the index of refraction of the gas is 1

The number of longitudinal modes within the gain bandwidth is 18.

Explanation:

Given that,

Wavelength = 488 nm

Frequency

Distance = 1 m

Index of refraction of the gas = 1

We need to calculate the number of longitudinal modes within the gain bandwidth

Using formula of number of longitudinal modes

Where, f = Doppler frequency

c = speed of light

l= separation

Put the value into the formula

Hence, The number of longitudinal modes within the gain bandwidth is 18.

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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.