Chapter 5 Light Energy Review

Vocabulary and key concepts from Chapter 5 on Light Energy, covering refraction, Snell's Laws, and dispersion.

Light

A form of energy which produces in us the sensation of sight, allowing us to see objects when light falls on them and is reflected into our eye.

Velocity of light in air or vacuum

$300000\,km/s$ or $3 \times 10^8\,ms^{-1}$.

Velocity of light in water

$2.25 \times 10^8\,m/s$ (given water density refractive index is $\mu = 1.33$).

Velocity of light in glass

$2 \times 10^8\,ms^{-1}$ (given glass is optically denser than water with $\mu = 1.5$).

REFRACTION OF LIGHT

The change in path that occurs as light travels from one transparent medium to another transparent medium and falls oblique at the second medium.

Refraction bending (Rarer to Denser)

When a ray of light travels from a RARER (less-denser) to a DENSER medium, it bends TOWARD the normal.

Refraction bending (Denser to Rarer)

When a ray of light travels from a DENSER to a RARER medium, it bends away from the NORMAL.

ANGLE of INCIDENCE ($\angle i$)

The angle which the incident ray makes with the normal.

ANGLE OF REFRACTION ($\angle r$)

The angle which the refracted ray makes with the normal; in refraction, $\angle i$ is not equal to $\angle r$.

SNELL'S LAWS OF REFRACTION

(i) Incident ray, normal at the point of incidence and Refracted ray all lie in the same plane. (ii) Ratio of sine of angle of incidence to the sine of angle of refraction is constant ($\frac{\sin(\angle i)}{\sin(\angle r)} = \text{Constant} = \mu$).

Refractive Index (R.I.) Formulas

$\text{R.I.} = \frac{\text{Speed of light in air}}{\text{Speed of light in medium}}$ or $\text{R.I.} = \frac{\text{Real depth}}{\text{Apparent depth}}$

Effects of Refraction

Includes a coin in water appearing raised, a swimming pool appearing SHALOW, a pencil in water appearing bent, MIRAGE in desert, EARLY Sunrise, and LATE SUN set.

White Light

A band of seven colours referred to as VIBGYOR, where all colours have the same speed in air or vacuum but different speeds in different transparent mediums.

VIOLET colour (in glass or water)

The color with MINIMUM speed and for which the Refractive index of the medium is minimum.

RED light (in glass or water)

The color with MAXIMUM speed and for which the R.I. of the medium is maximum.

DISPERSION OF LIGHT

The spliting (breaking) of white light into seven colours.

CAUSE OF DISPERSION

The speed of different colours is different in glass or water, causing different colours to separate from each other upon refraction at the second surface of a glass prism.