# Worksheet: Radiative Power of Electromagnetic Radiation

In this worksheet, we will practice determining the radiant power received per unit area at a distance from a point source of electromagnetic radiation.

**Q1: **

A point source of electromagnetic radiation has a radiant power of 225 W. The radiation emitted by the source is all visible light, with wavelengths between 400 nm and 700 nm. Each wavelength emitted has a 1 nm difference in length to its most similar emitted wavelength. All the wavelengths are emitted with the same energy. How much radiant power is emitted at each wavelength?

**Q2: **

Three point sources of electromagnetic radiation are at different points on the surface of a sphere centered on the point , as shown in the diagram. The radius of the sphere is 2.5 m. What is the irradiance at the point ?

**Q3: **

An object that emits electromagnetic radiation uniformly is at the position , as shown in the diagram. Which of the following statements most correctly describes how the irradiance produced by the radiating object at the points , , and on the surface of a sphere centered at compare to each other?

- A
- B
- C
- D
- E

**Q4: **

A point source emits electromagnetic radiation with a radiant power of 150 W. What is the irradiance at a point 2.4 m from the source?

**Q5: **

Which of the following formulas correctly relates the irradiance of electromagnetic radiation at a point to the distance from its source and the radiant power of the emitted electromagnetic radiation?

- A
- B
- C
- D
- E

**Q6: **

A point source emits electromagnetic radiation. The
irradiance at a point 3.43 m from the source is 1.75 W/m^{2}. What radiant
power does the source emit?

**Q7: **

Calculate the total irradiance at the point shown in the diagram due to the point sources of electromagnetic radiation.

**Q8: **

At a point , the irradiance due to the electromagnetic radiation emitted from a point source equals , where is the irradiance due to the same source at a point that is 15 cm from the source. How far from the source is ?

**Q9: **

A point source emits electromagnetic radiation with a radiant
power of 655 W. The irradiance at another point is 8.25 W/m^{2}. What is the distance of the point from the source?