Radio Station A - FM network using a radio wave of 93. 4 MHz (93 Radio Station A - FM network using a radio wave of 93.4 MHz (93.4 ×106 Hz) Radio Station B - AM network using a radio wave of 856 kHz Calculate the wavelength of each station When Zac is standing behind a hill, he can only tune into one of the two stations. Identify which station he can hear and explain why.

Station A: Wavelength = 3.21 m Station B: Wavelength = 350 m Zac will be able to hear station B because: the radio waves from Station B have longer wavelength which means it can diffract over the hill better than the radio waves from station A.

NCEA 2006 Q: Give a physics reason why Roy and Sally could hear the sound of the waves when they were sitting behind a building at the beach, even though they could not see the waves. A: This is because sound waves have a long wavelength. Light waves’ short wavelength means they will not be diffracted. (Merit)

The Properties of Waves Reflection Refraction Superposition Diffraction

Diffraction Bending of waves around a barrier or out through a gap The longer the wavelength, the more the diffraction of waves When passing through a gap, maximum diffraction occurs when the wavelength equals the size of the gap

The longer the wavelength, the more the diffraction

Gap – maximum diffraction occurs when the wavelength is equal to the size of the gap

Diffraction & Interference Pattern

What would happen if there are two gaps?

Dark Bright

Question What would happen to the pattern if; the screen is brought closer? the two gaps are further apart from each other? the frequency is increased?

If the screen is brought closer: The fringes will be closer together and brighter If the two gaps are further apart from each other: The fringes will be further apart If the frequency is increased: