What causes waves (in general)? What do waves transfer ?

1. What causes waves (in general)? What do waves transfer? • Waves are caused by vibrations • Pulse = single vibration • Oscillation – repeating vibration • ENERGY

2. 2. What does the period of a pendulum depend on? • The period (T) of a simple pendulum depends on: (1) length of the pendulum (2) acceleration due to gravity • It is NOT affected by the mass

3. 3. Label the parts of the waves: TRANSVERSE WAVE CREST WAVELENGTH (λ) AMPLITUDE TROUGH EXAMPLE: LIGHT

4. 3. Label the parts of the waves: LONGITUDINAL WAVE COMPRESSION RAREFRACTION WAVELENGTH (λ) EXAMPLE: SOUND

5. 4. Do longitudinal waves require a medium though which to travel? Do transverse waves? • Longitudinal waves DO require a medium. • Transverse waves DO NOT.

6. 5. What is the unit of measure of a wavelength? • Meters (m)

7. 6. If the amplitude of a wave is 5 m, how much is the top-to-bottom disturbance? • 10 m • Amplitude of crest (5 m) plus the amplitude of the trough (5 m).

8. 7. As waves dissipate what happens to the wave’s amplitude? • Amplitude decreases as the wave’s energy dissipates/turns into heat.

9. 8. What does frequency tell you? What is the unit of frequency? • The number of waves that pass a given point in a period of time (usually 1 second). • The unit is the Hertz (Hz)

10. 9. What is interference? What type of interference occurs when waves are in phase? Out of phase? • Interference is occurrence of multiple waves in the same place at the same time. • Waves in phase exhibit constructive interference / waves out of phase exhibit destructive interference.

11. 10. What causes the Doppler effect and when does it occur? • The Doppler effect is the observed shift in frequency caused by motion – either the source or the observer. • It occurs when objects move at a rate less than the speed of sound.

12. 11. What is the equation for wave speed? What are the units for wave speed? • v = λ x f • Units are meters/second (m/s)

13. 12. If a wave has a wavelength of 20 meters and a frequency of 0.5 Hz, what is speed?

14. 13. Does the speed of light change in a vacuum? What is the speed of light in a vacuum? • NO • The speed of light (c) = 3.00x108 m/s

15. 14. Light travels fastest through which phase of matter? Why is this? • Air, because the molecules in the air are the most spread out, therefore slowing light down less.

16. 15. How does the speed of light change when going from a gas to a liquid to a solid? • Light slows down when going from gas to liquid, and from liquid to solid (and vice versa).

17. 16. If a beam of light leaves water and moves into air, how is the beam bent? • As light speeds up when entering the air, the angle is bent away from the normal. • When moving from air into water (the reverse), the angle is bent toward the normal.

18. 17. What is reflection? • When a wave bounces off a material & goes in a new direction.

19. 18. What is refraction? • When a waves passes through a material & bends.

20. 19. What is diffraction? • When a wave bends around or passes through an opening in a material. • When plane waves go through an opening, they become circular waves

21. 20. What is an echo and what property of waves is responsible for it (reflection, refraction, diffraction)? • An echo occurs when a sound wave reflects off a distant surface / the observer hears the sound wave returning.

22. 21. What causes a rainbow? • Refraction of visible (white) light through a prism (in nature, rain droplets in the air)

23. 22. List all components of the elecromagnetic (EM) spectrum from lowest frequency to highest.

24. 23. If a light ray strikes a flat mirror at a given angle, at what angle will the reflected ray be? • An equal angle on the opposite side of the normal. • If the angle of incidence () is 39°, the angle of reflection () is ___39°___.

25. 24. What is a virtual image and how does it differ from a real image? • A virtual image is seen in the mirror (behind the mirror) – light rays DO NOT actually come together. • A real image is seen reflected back out of the mirror.

26. 25. Which type(s) of mirror(s) form a real image? Which form a virtual image? • REAL – Concave mirror (when object is behind the focal point) • VIRTUAL – Plane mirrors, Convex mirrors, & Concave mirrors (when object is in front of the focal point).

27. 26. When you look at a flat mirror, how do you see your image? • VIRTUAL & UPRIGHT

28. 27. When looking at a flat mirror from a distance of X m, your reflected image appears to be how far away from the mirror? How far is it from you? • Reflected image is X m away from the mirror. • The distance from you is 2X m.

29. 28. Why are ray diagrams used? • Ray diagrams are used to find out where an image will be located.

30. 29. What is the difference between red and blue light? • frequency (wavelength)

31. 30. Plane Mirror RAY 1 p q • VIRTUAL • UPRIGHT • SAME SIZE

32. 31. Concave Mirror – Behind Focal Point RAY 1 RAY 2 RAY 3 c f • REAL • INVERTED • SMALLER

33. 32. Concave Mirror – In Front of Focal Point RAY 1 RAY 2 RAY 3 c f • VIRTUAL • UPRIGHT • LARGER

34. 33. Convex Mirror RAY 1 RAY 2 RAY 3 f c • VIRTUAL • UPRIGHT • SMALLER

35. 34. Converging Lens RAY 1 RAY 2 RAY 3 f f • INVERTED • SAME SIZE

36. 35. Diverging Lens RAY 1 RAY 2 RAY 3 f f • REAL • UPRIGHT • SMALLER

37. 36. The lowest pitch that the average human can hear has a frequency of 20.0 Hz. If sound with this frequency travels through air with a speed of 331 m/s, what is its wavelength?

38. 37. Cicadas produce a buzzing sound that has a wavelength in air of 2.69 m. If the speed of sound in air is 346 m/s, what is the frequency of the sound produced by a cicada?

39. 37. (b) What is its period?

40. 38. A dolphin can typically hear sounds with frequencies up to 150 kHz. What is the speed of sound in water if a wave with this frequency has a wavelength of 1.0 cm?