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Matthew Schwartz. Lecture 19: Diffraction and resolution. 1 Huygens’ principle. Diffraction refers to what happens to a wave when it hits an obstacle. The key to understanding diffraction is a very simple observation first due to Huygens in 1678. Say a wave arrives at an opaque screen with a little hole in it.
A diffraction-limited eye with a 6 mm pupil is looking at an approaching car whose headlights have a wavelength of 550 nm and are separated by 1.5 m. What is the minimum angular resolution of the eye?
Lecture Video: Diffraction, Resolution. The phenomena related to diffraction are the focus of the lecture. Prof. Lee explains the mathematical description of the diffraction pattern of the wave traveling through a wide slit.
Interference is the combination of two or more waves to form a composite wave, based on such principle. The idea of the superposition principle is illustrated in Figure 14.1.1. (d) . Figure 14.1.1 Superposition of waves. (b) Constructive interference, and (c) destructive interference.
Diffraction also limits our ability to “resolve”(i.e., distinguish) two point sources. Consider two point sources (e.g., stars) with angular separation αviewed through a circular aperture or lens of diameter D .
Lecture 4, p 8 Q:What happens when a plane wave meets a small aperture? A: The result depends on the ratio of the wavelength λ to the size of the aperture, a: Huygens’principle A Consequence of Superposition λ >> a Similar to a wave from a point source. This effect is called diffraction. λ << a The transmitted wave is concentrated in the
Astronaut Joe is standing on a distant planet with binary suns. He wants to see them but knows it’s dangerous to look straight at them. So he decides to build a pinhole camera by poking a hole in a card. Light from both suns shines through the hole onto a second card.
