Inverse square law

Definition

The inverse square law states that the intensity of light or radiation from a point source decreases proportionally to the square of the distance from the source. This means if you double the distance, the intensity becomes one-fourth.

5 Must Know Facts For Your Next Test

1. The inverse square law applies to any point source of light, including stars and other celestial objects.
2. Mathematically, it is expressed as I ∝ 1/d², where I is intensity and d is distance.
3. This law explains why light from distant stars appears dimmer than closer ones.
4. It is crucial in determining luminosity and apparent brightness of astronomical objects.
5. The inverse square law also affects gravitational and electric forces just as it does light.

Review Questions

• How does doubling the distance from a light source affect its observed intensity?
• Write down the mathematical expression for the inverse square law.
• Why do we observe distant stars as dimmer compared to those that are closer?

Related terms

Luminosity:

The intrinsic brightness of a celestial object, independent of its distance from an observer.

Apparent Brightness:

The observed brightness of a celestial object as seen from Earth, dependent on its luminosity and distance.

Electromagnetic Spectrum:

The range of all types of electromagnetic radiation, including visible light, radio waves, X-rays, and others.