Question

I need help with question 9.

Velocity of light in air 3 x 10 ms Speed of sound in air 340 ms 5. a. Calculate the frequency of a wave in the visible spectrum of wavelength 600 nm. [2 b. The wave is incident upon a glass surface making an angle of incidence of 40. It is refracted at an angle of 25. Calculate: i. The refractive Index of glass. 2 ii. The velocity of light in the glass. 2 6 An object 10 cm high is placed 20 cm from a lens of focal length 12 cm. Calculate a. The power of the lens. [2 b. The distance from the lens to the position of the image. 2 c. The height of the image. 2 7, A string of length 1.2 m is set into vibration at its fundamental frequency of 480 Hz. Calculate a. The wavelength of the wave. [2 b. The velocity of the wave on the string. 1) 8. Explain what is meant by the terms with regards to standing waves a. Node. [1 b. Antinode. [1] 9. A closed pipe of length 0.80 m is made to vibrate at its third harmonic. a. Sketch the wave pattern of the note produced. b. Calculate the wavelength of the note produced. c. Calculate the frequency of the note produced.

Answer 1

Solution:

a)

AnhNode Anh Node に31

b) In thrid harmonic

=> wavelength = 4 x L / 3

=> wavelength = 4 x 0.80 / 3

=> wavelength = 1.067 m

c) frequcny

=> frequency = 3 x fundamenta frequency

=> Now we need to calculate fundamental frequency

=> fund. freq. = 340 / 4 x 0.80 ( velocity / 4L)

=> fund. freq = 106.25 Hz

Now frequency of third harmonic = 3 x 106.25

=> frequency = 318.75 Hz

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