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Chapter 7

LightLight

High frequency → High energy

Low energy → low frequency

Fig. 7.3

Speed of light = 3.0 x 108 m/s

Electromagneticradiation

Fig. 7.4 Blackbody radiation

According to Max Planck,According to Max Planck,

the energy of vibrating the energy of vibrating

molecules exists only inmolecules exists only in

multiples of certainmultiples of certain

fixed amountsfixed amounts

Fig. 7.11 The law of reflection

Fig. 7.12 A mirror produces a virtual image

A virtual imagecannot be projected

onto a screen

A real imagecan be projected

Fig. 7.13 Refraction (bending) of a light ray.

Fig. 7.14 Direction of refraction (bending) of light

Fig. 7.16 Formation of a mirage by bending of light

Our brains interpret the refracted light

as reflected light

Light travels faster in warmer air

Fig. 7.17 Roses are red because they reflect red light

Box Fig. 7.1 Two types of lenses

Converging lens

Diverging lens

Box Fig. 7.3 The human eye

Box Fig. 7.4 accomodation

Box Fig. 7.7 How a rainbow is formed

light is refracted

with blue being refracted

more than red is refracted

White

ROYGIBIV

Fig. 7.18 Young’s double-slit experiment

Interference pattern

Fig. 7.19 Polarization of light

Consider light to betransverse waves

Fig. 7.20 Two ways to position two polaraizers

Fig. 7.21 Reflected light may be polarized

Fig. 7.22 The photoelectric effect

Explanation by Einstein:

Light must strike metal

as small particles (quanta)

Light intensity has noeffect on the energy ofthe ejected electrons

Ephoton = hf

h = Planck’s constant

= 6.63 x 10-34 J

photons

Fig. 7.23 Light is both a wave and a particle