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Lesson: Radiation Pressure on Perfectly Reflective Surfaces Physics

In this lesson, we will learn how to calculate the pressure exerted on an object by light that is reflected by it.

Lesson Plan

Students will be able to

recognize that light exerts a pressure,
recognize that the pressure exerted by light is greater if the light is reflected than if it is absorbed,
use to find the pressure exerted by light of a given intensity that is reflected off a surface,
use to find the force exerted by light of a given intensity that is reflected off a surface with area .

Lesson Presentation

Lesson Video

Lesson Explainer

Lesson Worksheet

Q1:

Which of the lines on the graph shows how the pressure exerted by radiation being reflected by a surface varies with the intensity of the radiation?

Q2:

Light with an intensity of 50.0 W/m² is directed at a ‎ reflective surface. The surface has an area of 2.25 m². What force is exerted by the light on the surface? Use a value of m/s for the speed of light in a vacuum.

Q3:

Light of constant intensity is directed at a ‎ reflective surface. The light strikes the surface at an angle, as shown in the diagram. If , will the radiation pressure exerted by the light on the surface be greater than, less than, or equal to the radiation pressure when ?