Dispersion and the spectrum
A prism splits white light into colours.
A beam through glass
A narrow beam of white sunlight goes through a triangular glass prism and falls on a wall.
What do you expect to see on the wall?
What this lesson covers
The idea
A prism splits white light into a band of colours, its spectrum, in the sequence violet, indigo, blue, green, yellow, orange, red (VIBGYOR); this splitting of light into its component colours is dispersion.
A beam through glass
A narrow beam of white sunlight goes through a triangular glass prism and falls on a wall.
What do you expect to see on the wall?
- A band of many colours
- A single white spot
- A single red spot
White light into a prism
Press Next step.
Seven colours
The prism spreads white light into a band of colours. We remember their order by the word VIBGYOR. The band is the spectrum, and the splitting is called dispersion.
A prism splits white light into a band of colours, its spectrum, in the sequence violet, indigo, blue, green, yellow, orange, red (VIBGYOR); this splitting of light into its component colours is dispersion.
Notes
A prism splits white light into its spectrum, violet, indigo, blue, green, yellow, orange, red (VIBGYOR). This splitting of light into colours is dispersion.
Check yourself
The band of coloured components of a light beam is called its…
The splitting of light into its component colours is called…
Which sequence of colours is correct (VIBGYOR)?
Into how many colours does a prism split white light, as listed in VIBGYOR?
Answer: 7
Violet, indigo, blue, green, yellow, orange and red make seven colours.
- dispersion. Dispersion is the splitting of light into its component colours. The band of colours is the spectrum.
- spectrum — correct. Yes!
- deviation. The angle of deviation is the angle between the incident and emergent rays, not the band of colours.
- the spectrum. The spectrum is the band of colours that results.
- the angle of the prism. The angle of the prism is the angle between two lateral faces.
- dispersion — correct. Yes!
- Violet, indigo, blue, green, yellow, orange, red — correct. Yes!
- Red, orange, yellow, green, blue, indigo, violet. That is the reverse order. VIBGYOR starts with violet and ends with red.
- Violet, blue, indigo, green, yellow, red, orange. The order is violet, indigo, blue, green, yellow, orange, red.