Module 2:WAVES AROUND YOU

Archie A. Duran

Waves are all around us…Throwing a stone into a lake

Strumming the strings of a guitar

Switching on of a lamp

Water wavesSound wavesLight waves

Importance of Waves Helps explain phenomena in nature Helps in designing skyscrapers and bridges

Helps in improving telecommunication and technology

What is a WAVE??? a wave is a periodic disturbance that moves away from the source and carries energy

regularmovement

Activity 1: Let’s make wavesObjective

In this activity, you will observe and draw different types of waves and describe how they are produced. You will also describe the different types of waves.

3 types of Waves

Transverse WavesLongitudinal WavesSurface Waves

transverse perpendicul

ar

longitudinal

circular

Anatomy of a Wave

CrestTroughAmplitudeWavelength

Crest The highest points of a wave.

Trough Lowest points of a wave.

Amplitude The maximum displacement of a wave from the equilibrium.

Wavelength Distance from two successive crest or trough.

Frequency vs. Period

Frequency The number of waves that pass a reference point for one second.

Units: 1 cycle/second = 1 Hertz

Period The time needed for one complete wave to pass a reference point.

Unit: seconds

Frequency-Period Relationship Frequency is the reciprocal of period

Period is the reciprocal of frequency𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦=

1𝑝𝑒𝑟𝑖𝑜𝑑 𝑃𝑒𝑟𝑖𝑜𝑑=

1𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦

Sample Problems

A young girl is on a swing that completes 20.0 cycles in 25 seconds. What are its frequency and period?

A clock clicks 88 times in 22 seconds. Calculate the frequency and period of the clock.

A spring vibrates 24, 000 times in 1.00 minutes. What are the frequency and period. [Hint: frequency is cycles per second.]

Wave Speed The distance travelled of a wave per unit of time.

Distance = wavelength Time = Period

or

𝑊𝑎𝑣𝑒𝑆𝑝𝑒𝑒𝑑=h𝑊𝑎𝑣𝑒𝑙𝑒𝑛𝑔𝑡

𝑃𝑒𝑟𝑖𝑜𝑑

𝑊𝑎𝑣𝑒𝑆𝑝𝑒𝑒𝑑= h𝑊𝑎𝑣𝑒𝑙𝑒𝑛𝑔𝑡 𝑥 𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦

Examples

A vibrating source with a frequency of 20.0 Hz produces water waves that have a wavelength of 3.0 cm. Calculate the speed of the waves.

A wave along a guitar string has a frequency of 540 Hz and a wavelength of 2.5 meters. Calculate the speed of the wave.

Relationship between

wavelength, wave speed,

frequency, and energy.

As wavelength increases, wave speed ____________.

As wavelength decreases, wave speed ____________.

As wavelength increases, frequency __________.

As wavelength decrease, frequency __________.

As frequency increases, wave speed ____________.

As frequency decreases, wave speed ____________.

Mechanical Wavesvs.

Electromagnetic Waves

Mechanical Waves Are waves the can only be transmitted

with the presence of a medium.

Medium can be solids, liquids, or gas

Ex. Sound waves, seismic waves, water waves

Electromagnetic Waves Are waves that can be transmitted even without the presence of a medium.

Ex. Radiowaves, x-ray, microwave, UV waves, infrared waves, visible light waves

Mental Exercise...

1. What happens to energy as wavelength increases?

2. As wave speed

decreases, wavelength

_______________.

3. What happens to

frequency as wave speed increases?

4. As wavelength decreases, wave speed

________________.

5. As energy increases,

what happens to wave speed?

6-7. Give the 2 formula used in computing wave speed.

8-10. Give the 3 classification of waves based on the motion of wave from its

source.

11. Frequency is said to be

the reciprocal of _____________.

12. The highest points of a wave are

known as ________________.

13. The distance from crest to the next crest is

known as ________________.

14-15. Give the 2

classification of wave based

on the requirement for medium.

Next Module: SOUND Wave