Question

Кусочек металлической фольги массой 1 мг освещается лазерным импульсом мощностью 15 Вт и длительностью 0,5 с. Свет падает нормально плоскости фольги и полностью отражается от нее в обратном направлении. Определить скорость, приобретенную фольгой в результате действия света.

Answer 1

1) импульс фотона P1=h/л

2) изменение импульса одного фотона  2*h/л

3) число падающих фотонов N=P*t/E1   E1=h*c/л
N=P*t*л/h*c
4) изменение импульса пылинки  N*P1=m*V

m*V=2*P*t/c
V=2*P*t/m*c=2*15*0,5/10^-6*3*10^8=0,05 м/с

Answer 2

Calculation of the Speed Acquired by the Foil

To determine the speed acquired by the foil as a result of the light's action, we can use the principle of conservation of momentum. The momentum of an object is given by the product of its mass and velocity.

The laser pulse with a power of 15 W and a duration of 0.5 s illuminates the foil. The light falls normally on the surface of the foil and is completely reflected in the opposite direction. We need to calculate the velocity acquired by the foil.

To calculate the velocity, we can use the equation:

Momentum before = Momentum after

The momentum before the light hits the foil is zero since the foil is initially at rest. The momentum after the light is reflected is given by the product of the mass of the foil and its velocity.

Let's assume the mass of the foil is 1 mg (0.001 g).

Using the equation for momentum:

0 = (mass of the foil) x (velocity of the foil)

We can rearrange the equation to solve for the velocity:

Velocity of the foil = 0 / (mass of the foil)

Substituting the mass of the foil:

Velocity of the foil = 0 / 0.001 g

Since any number divided by zero is undefined, the velocity acquired by the foil is undefined.

Therefore, the foil does not acquire any velocity as a result of the light's action.