6.2.5 Visible Light

In this lesson, we will delve into the properties and characteristics of visible light. We will learn about the specific wavelengths and frequencies associated with different colours within the visible light spectrum.

The Visible Light Spectrum

Visible light is made up of different colours, each with its own narrow band of wavelengths and frequencies. The visible light spectrum spans from longer wavelengths (red light) to shorter wavelengths (violet light).

Specular and Diffuse Reflection

• Specular Reflection: Reflection from a smooth surface occurs in a single direction, resulting in a clear reflection of light. This is known as specular reflection.
• Diffuse Reflection: Reflection from a rough surface causes light to scatter in multiple directions, resulting in a diffused reflection.

Colour Filters

• Colour filters are designed to selectively absorb certain wavelengths (colours) of light while transmitting others.
• By absorbing specific colours and allowing only certain wavelengths to pass through, colour filters can modify the perceived colour of light or objects.

Absorption, Reflection, and Transmission

• The colour of an opaque object is determined by the wavelengths of light it reflects more strongly.
• Absorption: Objects absorb wavelengths of light that are not reflected, contributing to the perceived colour.
• Reflection: The wavelengths that are reflected from an object contribute to its observed colour.
• Transmission: Transparent or translucent objects allow light to pass through, either partially or completely, resulting in different levels of transmission.

Effects of Filters on Light

• Viewing Objects through Filters: Filters alter the wavelengths of light that reach our eyes, affecting the perceived colour of objects.
• Effects of Light Passing through Filters: When light passes through a filter, certain wavelengths are absorbed, while others are transmitted, resulting in a modification of the light's colour.

Opaque Object Colours

• The colour of an opaque object depends on the differential absorption, transmission, and reflection of different wavelengths of light.
• If an object reflects all wavelengths equally, it appears white. If all wavelengths are absorbed, the object appears black.
• Objects that reflect certain wavelengths more strongly than others exhibit a specific colour based on the wavelengths that dominate the reflected light.

Conclusion

Visible light comprises different colours, each with its own unique wavelength and frequency. Reflection can occur in either a specular or diffuse manner, depending on the surface characteristics. Colour filters selectively absorb and transmit specific wavelengths, modifying the perceived colour of light or objects. The colour of an opaque object is determined by its differential absorption, transmission, and reflection of different wavelengths. Transparent or translucent objects transmit light, with varying degrees of transparency.