Refraction of Light Lecture Notes

Vocabulary flashcards covering optical density, the speed of light in various mediums, refraction principles, refractive indices, the twinkling of stars, and the conditions and applications of total internal reflection.

Optical density

The ability of a medium to influence the speed of light through the medium.

Optically denser medium

A medium where the speed of light is lower due to a higher optical density.

Optically rarer medium

A medium where the speed of light is higher due to a lower optical density.

Refraction

The phenomenon where a ray of light undergoes a deviation at the surface of separation when it enters obliquely from one medium to another of different optical densities.

Refractive index ($n$)

The ratio of the speed of light in vaccum ($c$) to the speed of light in the medium ($v$), represented by the formula $n = \frac{c}{v}$.

Speed of light in vaccum ($c$)

$$3 \times 10^8 \text{ m/s}$$

Speed of light in water

$$2.25 \times 10^8 \text{ m/s}$$

Speed of light in Glass

$$2 \times 10^8 \text{ m/s}$$

Speed of light in Diamond

$$1.25 \times 10^8 \text{ m/s}$$

Refractive index of water (per transcript calculation)

$0.75$ (calculated as $\frac{3 \times 10^8 \text{ m/s}}{2.25 \times 10^8 \text{ m/s}}$).

Refractive index of Glass

$\frac{3}{2}$ (calculated as $\frac{3 \times 10^8 \text{ m/s}}{2 \times 10^8 \text{ m/s}}$).

Rare medium to denser medium deviation

When light enters obliquely from an optically rarer medium to a denser medium, it deviates towards the normal.

Denser medium to rarer medium deviation

When light enters obliquely from an optically denser medium to a rarer medium, it deviates away from the normal.

Normal incidence refraction

A ray incident normally at the surface of separation of mediums does not undergo refraction.

Twinkling of star

The result of irregular refraction as light from stars reaches the eye after traversing atmospheric layers with continuously changing physical conditions like pressure and temperature.

Critical angle

The angle of incidence at which the angle of refraction becomes $90^\text{o}$; for the glass-air pair, it is $42^\text{o}$.

Total internal reflection

The phenomenon where a ray enters from an optically denser medium to a rarer medium at an angle of incidence greater than the critical angle, and the ray is reflected back completely to the same medium without refraction.

Applications of Total internal reflection

In reflectors, in periscopes, and in optical fibre.

Laws of reflection

$\text{Angle of incidence (i)} = \text{Angle of reflection (r)}$ (written as $i = r$).

Angle of incidence ($i$)

The angle between the incident ray and the normal.

Angle of reflection ($r$)

The angle between the reflected ray and the normal.