Unit 07 WAVES WAVE PROPERTIES SOUND WAVES LIGHT

Unit 07 WAVES & WAVE PROPERTIES SOUND WAVES & LIGHT WAVES PROBLEM SOLVING

REVIEW Wave Speed Equation V=f λ velocity = frequency x wavelength c =f λ Speed of light = frequency x wavelength

Sound needs a medium to travel Speed of Sound in standard air: v = 340 m/s Light can travel through a vacuum Speed of Light in a vacuum: c = 300, 000 m/s

What is the relationship between speed, frequency and wavelength? � The only way to change the speed of the wave is To change the medium to ____________. �A change in the frequency will change wavelength _______. �A change in the wavelength will change frequency ______.

Easier Problem Solving 1. A guitar emits frequencies that range from a low of about 50 Hz to a high of about 3000 Hz. Find the range of wavelengths in air attained by this instrument when the speed of sound is air is 340 m/s.

Easier Problem Solving 1. A guitar emits frequencies that range from a low of about 50 Hz to a high of about 3000 Hz. Find the range of wavelengths in air attained by this instrument when the speed of sound is air is 340 m/s. V = 340 m/s f = 50 Hz λ=? V=f λ 340 m/s = 50 Hz(λ) 50 Hz 6. 8 m = (λ) V = 340 m/s f = 3000 Hz λ=? Range: 0. 113 m – 6. 8 m V=f λ 340 m/s = 3000 Hz(λ) 3000 Hz 0. 113 m = (λ)

Mediumier Problem Solving 2. What is the frequency of a red light with a wavelength of 650 nm. (remember, the speed of light is 3 x 108 m/s)

Mediumier Problem Solving 2. What is the frequency of a red light with a wavelength of 650 nm. (remember, the speed of light is 3 x 108 m/s) c = 300, 000 m/s f =? 650 nm x 10 -9 m = 6. 50 x 10 -7 m λ = 650 nm 1 nm (0. 000000650 m) c =f λ 30000 m/s = f (6. 50 x 107 m) 6. 50 x 10 -7 m 4. 62 x 1014= f

Mediumier Problem Solving 3. What is the wavelength of the FM radio station “ 94. 5 HJY” --- its frequency is 94. 5 MHz.

Mediumier Problem Solving 3. What is the wavelength of the FM radio station “ 94. 5 HJY” --- its frequency is 94. 5 MHz. c = 3 x 108 m/s f = 94. 5 MHz 94. 5 MHz x 106 Hz = 94. 5 x 106 Hz (or 9. 45 x 107 Hz) λ=? 1 MHz c =f λ 3 x 108 m/s = (94. 5 x 106 Hz) λ 94. 5 x 106 Hz 3. 17 m = λ

1. What is the minimum frequency of sound waves required for the bat to detect an insect that would reflect a wavelength of 0. 0057 m? (Assume the speed of sound is 340 m/s). The answer should be f = 59649 Hz 2. The red light emitted by a He-Ne laser has a wavelength of 633 nm in air and travels at 3. 00 x 108 m/s. Find the frequency of the laser light. The answer should be f = 4. 74 x 1019 Hz 3. What is the frequency of a sound wave produced by a flute playing Cnote if the wavelength is 21 m? The answer should be f = 16. 2 Hz 1. What is the wavelength of a radar signal that has a frequency of 33 GHz? The answer should be λ= 0. 00909 m

PRACTICE � COMPLETE THE ATTACHED WORKSHEET. � PLEASE NOTE: � The Period (T) represents the time it takes one point in a wave to travel one wavelength. T=1/f � Velocity is the rate of change in an object’s position. V=d/t (with d being the distance travelled)