A diffraction grating having diffracts visible light at . What is the light's wavelength?
The wavelength of sunshine is
The constant value of grating is ,the spacing by
In equation of grating,the light diffraction light wavelength by
From expression of wavelength
As we're seeing, there should only be one value of that corresponds to a wavelength within the visible region and therfore the will be ,The wavelength are .
The pinhole camera of FIGURE images distant objects by allowing only a narrow bundle of light rays to pass through the hole and strike the film. If light consisted of particles, you could make the image sharper and sharper (at the expense of getting dimmer and dimmer) by making the aperture smaller and smaller. In practice, diffraction of light by the circular aperture limits the maximum sharpness that can be obtained. Consider two distant points of light, such as two distant streetlights. Each will produce a circular diffraction pattern on the film. The two images can just barely be resolved if the central maximum of one image falls on the first dark fringe of the other image. (This is called Rayleigh’s criterion, and we will explore its implication for optical instruments in Chapter .)
a. Optimum sharpness of one image occurs when the diameter of the central maximum equals the diameter of the pinhole. What is the optimum hole size for a pinhole camera in which the film is behind the hole? Assume an average value for visible light.
b. For this hole size, what is the angle a (in degrees) between two distant sources that can barely be resolved?
c. What is the distance between two street lights away that can barely be resolved?
A 600 line/mm diffraction grating is in an empty aquarium tank. The index of refraction of the glass walls is . A helium-neon laser is outside the aquarium. The laser beam passes through the glass wall and illuminates the diffraction grating.
a. What is the first-order diffraction angle of the laser beam?
b. What is the first-order diffraction angle of the laser beam after the aquarium is filled with water ?
It shows the light intensity on a viewing screen behind a circular aperture. What happens to the width of the central maximum if the
a. The wavelength of the light is increased.
b. The diameter of the aperture is increased.
c. How will the screen appear if the aperture diameter is less than the light wavelength?
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