The document discusses how a glass prism refracts white light into a visible spectrum. It explains that when white light enters a prism, the different wavelengths of light are refracted by different amounts due to dispersion. This causes the light to separate into the colors of the visible spectrum from red to violet. An experiment is described where a beam of white light passes through a prism, producing a spectrum that can be used to measure the angles of refraction and dispersion.

1. Transparent Glass Prism
LI
GHT

2. Prism and refraction
A
δm
N N
Prism
A is the angle of prism
N is normal on the surface of prism
δm is the deviation of emerging ray from initial direction

3. Dispersion of white light of sun by prism
Red 6600 Å
Orange 6100 Å
Yellow 5800 Å
Green 5500 Å
Blue 4700 Å
Indigo 4400 Å
Violet 4100 Å
Spectrum
A
prism
wavelength λ of the center of color band in angstroms
If a shaft of light entering a prism is sufficiently small such
that the coloured edges meet, a spectrum results

4. An experiment to observe spectrum
white light Spectrum

5. δR δV
Θ
A
δm ⇒ mean deviation or deviation
for yellow
Angle of dispersion θ
θ = δV - δR
Dispersive power ω
θ
δm
ω =
δm
ω =
δV - δR
Deviation by prism
δR ⇒ deviation for red
δV ⇒ deviation for violet
δm