Physics 1051: Lecture 4: Slide 1

Light Introduction

Physics 1051: Lecture 4: Slide 2

Light -- an Electromagnetic Wave

Physics 1051: Lecture 4: Slide 3

Electromagnetic Wave

• Transverse• Traveling oscillating

electric field and magnetic field

• Can travel through space

• Generated by accelerated charges

• Emitted by excited atoms when they return to ground state

Physics 1051: Lecture 4: Slide 4

Electromagnetic Spectrum

Physics 1051: Lecture 4: Slide 5

Physics 1051: Lecture 4: Slide 6

Visible Part of Spectrum

7 4

Physics 1051: Lecture 4: Slide 7

Spring Model• Electrons can be

modeled as particles connected to the atomic nucleus by springs

• Electrons of atoms in glass have certain natural frequencies of vibration

Physics 1051: Lecture 4: Slide 8

Light Transmission

Physics 1051: Lecture 4: Slide 9

Glass Transparency

Ultraviolet matches natural frequency of electrons in glass

Infrared vibrates entire atom or molecule

Both result in warming of the glass

Physics 1051: Lecture 4: Slide 10

Opaque

• What does it mean for an object to be opaque?

• Light is absorbed without being re-emitted.

Physics 1051: Lecture 4: Slide 11

Umbra to Penumbra

Physics 1051: Lecture 4: Slide 12

Solar Eclipse

Physics 1051: Lecture 4: Slide 13

Physics 1051: Lecture 4: Slide 14

Physics 1051: Lecture 4: Slide 15

Moon’s Orbit is Tilted

Physics 1051: Lecture 4: Slide 16

The Eye