Physics – Semester 2 – Waves, Electricity, and Light

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Things for Class... Please bring a pencil, pen, highlighter,

straight edge, paper, and scientific calculator to class every day

I will provide you with graph paper and a textbook

Let’s take notes… The notes you take in class are for yourself. Practice taking notes in a style that works for you

(Cornell, draw pictures and diagrams, clouds, flowchart, etc)

Review your notes daily

Exams Topics Exam I - Sound Chapters 19, 20, 21 Exam II – Electricity and Magnetism Chapters 23, 24, 25 Exam III - Light Chapters 26, 27, 28, 29, 30

Final Exam

Chapter 19Vibrations and

Waves

Vibrations and Waves

Oar in Water Wings of a Bee Electrons in an

Light Bulb

Water Waves Sound Waves Light Waves

Vibrations and Waves

Waves transmit energy and information.

Sound and Light are both waves.

Simple Harmonic Motion... …is to-and-fro (back and forth) vibratory

motion.

...results in sine curves.

Examples: metronome mass on a spring pendulum

Pendulums & Galileo The period does not depend on the amount of

mass. The period does depend on the length of the

pendulum.

T l g 2T = period l = length of pendulum

g = gravity

Wave Description

Period - the time required for one vibration

measured in seconds

Frequency - number of vibrations per unit time

measured in Hertz

Wave Description

FrequencyPeriod

1

PeriodFrequency

1

Example Test Question:If you double the frequency of a vibrating object, what happens to the period?

a) the period doublesb) the period stays the samec) the period is cut in halfd) not enough information is given to answer this question.

*

What is the frequency in vibrations per second of a 60-Hz wave?

Answer: 60 cycles per second

What is its period?Answer: 1/60 second

Sine Curves Amplitude - distance from the baseline to the

crest of a wave

Wavelength - the distance from the top of one crest to the top of the next one

Wavelength (λ)

Example Test QuestionsAnswer these questions using the sine wave provided.

1. What is the amplitude of the wave?

3. What is its wavelength?

2 ½ meters

20 cm

Wavelength = 1 m

Example Wave

Amplitude = 10 cm

Wave Motion medium - the stuff that carries the wave

Waves Mediumwater waves water

waves on a rope rope

stadium waves people

sound air

light space (vacuum)

Wave Speed... the speed with which waves pass by a

particular point e.g. the speed of a surfer

It depends only on the type of medium.

Wave Speed = Frequency Wavelength v = f x λ

If a water wave oscillated up and down three times each second and the distance between wave crest is 2 m, what is its frequency?

Answer: 3 Hz

What is its period?

Answer: 1/3 second

What is its wavelength?

Answer: 2 m

What is its wave speed?

Answer: 6 m/s

End of Part 1