The brightness of a light wave depends on its intensity. Intensity is a measure of the amount of light energy emitted by a light source per unit area per unit time. It is measured in watts per square meter (W/m²). The higher the intensity of a light wave, the brighter it will appear.

Intensity is affected by a number of factors, including the power of the light source, the distance from the light source, and the angle at which the light hits the surface. The power of a light source is measured in watts. The higher the wattage, the more intense the light will be. The distance from the light source also affects intensity. The farther away from the light source, the less intense the light will be. This is because the light energy spreads out as it travels, so the intensity decreases with distance. Finally, the angle at which the light hits the surface can also affect intensity. Light that hits a surface at a right angle will be more intense than light that hits the surface at an angle. This is because the light energy is concentrated in a smaller area when it hits the surface at a right angle.