Apparent depth of an object underwater

In summary, the conversation discusses how to solve a problem involving Snell's law and the approximation ##\sin(\theta)\approx\tan(\theta)## for small theta. However, without the information of where the light will come out on the surface of the water, the problem becomes more complex. The solution involves finding the two angles as functions of x, with an estimated value of ##x\approx 18\ m## and an apparent depth of ##d'\approx 0.19\ m##.
  • #1
lorenz0
148
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Homework Statement
A person (the arrow at the upper left of the figure) of height ##h=1.7m## is standing at the edge of a pool of water of depth ##d=1.8m## in which there is an object located at the farthest end of the pool (black ball in the figure). What is the apparent depth of this object for the person looking at the pool, i.e. what is the depth of the object observed by the person (red ball in the figure)?
Relevant Equations
##n_1 \sin(\theta_1)=n_2\sin(\theta_2)##
I would know how to solve this problem if the person had been standing pratically above of the object underwater by using Snell's law and the approximation ##\sin(\theta)\approx\tan(\theta)## fopr ##\theta## small, but in this case I don't see how to find the angles ##\theta_1## and ##\theta_2## and, above all, at what point along the surface of the water the light with come out in such a way as to reach the eye of the person. Without this last information, when I try to set up Snell's law I get (with ##x## representing the distance from the left corner at which the light comes out): ## \frac{d^2+(L-x)^2}{d'^2+(L-x)^2}=1.33^2 ## but I have too many variables.

So, I would appreciate if someone could point me twoards a viable strategy to solve this problem. Thanks
 

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  • #2
Find the two angles as functions of x.
 
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Likes lorenz0
  • #3
haruspex said:
Find the two angles as functions of x.
Thanks. I got ##x\approx 18\ m## and an apparent depth of ##d'\approx 0.19\ m##.
 
  • #4
lorenz0 said:
Thanks. I got ##x\approx 18\ m## and an apparent depth of ##d'\approx 0.19\ m##.
That looks right.
 

1. What is the apparent depth of an object underwater?

The apparent depth of an object underwater is the distance between the observer's eye and the object, as it appears to the observer. This can be different from the actual depth of the object due to the refraction of light in water.

2. How does the refraction of light affect the apparent depth of an object underwater?

The refraction of light in water causes the light rays to bend as they pass from air to water, making the object appear closer and shallower than it actually is. This is why objects underwater may appear closer or larger than they really are.

3. Does the apparent depth of an object underwater change with the depth of the water?

Yes, the apparent depth of an object underwater does change with the depth of the water. As the water gets deeper, the refraction of light becomes stronger, causing the object to appear even shallower than it actually is.

4. How does the angle of observation affect the apparent depth of an object underwater?

The angle of observation, or the angle at which the observer is looking at the object, also affects the apparent depth. The closer the observer is to the surface of the water, the greater the refraction of light and the shallower the object will appear.

5. Can the apparent depth of an object underwater be calculated?

Yes, the apparent depth of an object underwater can be calculated using the Snell's law, which relates the angles of incidence and refraction of light in water. This can be useful for divers or scientists studying objects underwater.

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