Conversely, an object above the water has a higher apparent height when viewed from below the water. This is an important consideration for spearfishing from the surface because it will make the target fish appear to be in a different place, and the fisher must aim lower to catch the fish. The depth that the water appears to be when viewed from above is known as the apparent depth. This causes the pencil to appear higher and the water to appear shallower than it really is. The lines of sight (shown as dashed lines) intersect at a higher position than where the actual rays originated. Once the rays reach the eye, the eye traces them back as straight lines (lines of sight). This is due to the bending of light rays as they move from the water to the air. Looking at a straight object, such as a pencil in the figure here, which is placed at a slant, partially in the water, the object appears to bend at the water's surface. Refraction occurs when light goes through a water surface since water has a refractive index of 1.33 and air has a refractive index of about 1. Refraction in a water surfaceĪ pencil part immersed in water looks bent due to refraction: the light waves from X change direction and so seem to originate at Y. How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed.įor light, refraction follows Snell's law, which states that, for a given pair of media, the ratio of the sines of the angle of incidence θ 1 and angle of refraction θ 2 is equal to the ratio of phase velocities ( v 1 / v 2) in the two media, or equivalently, to the refractive indices ( n 2 / n 1) of the two media. Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction. The redirection can be caused by the wave's change in speed or by a change in the medium. In physics, refraction is the redirection of a wave as it passes from one medium to another. You are also right for refraction, wavelength varies, not frequency, and the changing wavelength leads to a different velocity.A ray of light being refracted in a plastic block. You are right on for dispersion, in (very) short, you exploit the different indexes of refraction to break up the different components of light. If you get confused about diffraction especially, imagine light as particles instead of waves, it may make more sense to you, I believe that diffraction was actually a proof for the big wave vs particle debate, and pretty much the explanation that was put out was that at the edges of the slit, the photons of light collided which resulted in them 'fanning out'. I think that the wavelength stays the same for the light, since the equations involved imply that the wavelength stays constant throughout, then I don't think that wavelength changes, and since I don't think that frequency changes either, velocity stays the same. It is simply a phenomenon that occurs when light passes through a slit or a narrow opening. I don't think that diffraction is actually the velocity of the light changing. What's the difference between dispersion and refraction then? This means: velocity will change wavelength will change f remains the same ? this is just my thought. Diffraction: happens when waves (light) encounter an obstacle This means: velocity will change wavelength will change frequency remains the sameĢ>. Refraction: occurs when waves travel and encounter a boundary (i.e. Need help with the concept of these 3 items:ġ>.
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