1. Waves

2. How measured? Wavelength: length of complete cycle
Frequency: number of cycles per unit time
Amplitude: distance covered by a particle

3. Two Types
Transverse Wave
Longitudinal Wave

4. Calculating frequency
Measured in Hertz(Hz)
Number of cycles per unit of time
f = Number of cycles
Total time
Speed = frequency x wavelength

5. Ex. What is the frequency of the wave below?
a)What is the frequency of the wave if this movement took 0.5 seconds? b) What is the speed of the wave?

6. a) f = 2 cycles/ 0.5 sec. f = 4 cycles/s b) Speed = frequency x wavelength = 4 cycles/s x 40 cm = 160 cm/s Do # 5 p. 11 7

7. 1. Mechanical Waves Requires a medium to propagate
Sounds waves: longitudinal & mechanical, decibel scale (db)

8. Sound Waves
Variations in air pressure cause the sound wave to move through the air (medium)
Ex. Loudspeakers, musical instruments, thunder

9. Frequency and sound - Sounds can have different tones
Range of sound perception changes with each animal (see p.104)
Low Frequency sounds = low pitched sound ex. Bass player
High Frequency sounds = high pitched sound
ex. Siren, birds chirping
Unit of sound frequency : Hertz (Hz)
Teen buzz Hz to Hz
(30’s & over: hard to hear over Hz)

10. Amplitude Intensity of Sound depends on:
The Amplitude (loudness of the sound)
Measured in: decibels (dB)
Sound tones: frequency in Hertz (Hz)

12. Decibel Scale
Scale is a relative scale that represents the perception of the intensity of sound by the human ear.
Measured: by a factor of 10
Each increase of 10, sound is 10 times louder
Ex. Human breathing 10dB
Soft music dB
50-10= 40
So, 10 x 10 x 10 x 10 = times louder!

13. 2. Electromagnetic Waves
Can travel in a vacuum or a medium.
Includes visible light
Includes radio waves, x-rays etc.
Wavelength: short wavelength, higher frequency ( high energy!)
ex. Gamma rays
Long wavelength, lower frequency (low energy!)
ex. Radio wave

15. Light Travels in straight lines(electromagnetic, transverse)
An electromagnetic wave that is visible to the human eye.

16. Reflection
1. Diffuse reflection: uneven surfaces, scatter light

17. Specular reflection: - smooth surfaces
- laws of reflection apply
“angle of incidence=angle or reflection”

18. Real vs. Virtual Image Real image can be projected on a screen
Virtual images cannot be projected on a screen

19. Refraction Light changes direction when it passes
from one substance to another.
(light is deviated as it passes)
Why?
- Speed of light depends of the medium
it passes through
- speed of light changes as it passes
from air to water

20. Refracted light rays

21. Lenses
Light refracts as it passes through lenses
Two types of lenses

22. 1. Converging lenses Brings light rays together Thickest at centre.
Show light as ray in diagram
Focal point real point where
light meets at far side of lens
Second Principal Focus:
same distance on other side
of lens

23. 2. Diverging Lenses Spread light rays apart Thinnest at centre.
Focal point: virtual point
where light appears to
emanate

24. Convex(converging) & Concave (Diverging)

25. How does this relate to the eye?
Accommodation of crystalline lens of eye:
a) far away object: - lens stretches, flatten
- distant light rays don’t need as
much refraction
b) near object: - lens shortens, more spherical
- light from near objects need to
be refracted more

27. Corrective lens:
a) myopia (nearsighted): diverging lens moves image back
towards retina
b) hyperopia (farsighted): converging lens moves images
forward onto retina