Refraction - when can you see past the label?

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In summary, the problem involves a glass surface with a critical angle of 41.8 degrees, and a circular label placed above a spot on the surface. This means that light rays striking the surface at an angle less than the critical angle will be refracted into the glass, making the spot visible. However, if the light ray strikes at an angle greater than the critical angle, it will be totally reflected and the spot will not be visible to an observer in any direction. The position of the observer is not given in the problem.
  • #1
jadelamlam
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refraction -- when can you see past the label?

Homework Statement


as shown in the figure.


Homework Equations


n1sin1 = n2sin2
n1 and n2 represent the refractive indices of media 1 and 2 respectively

The Attempt at a Solution


Critical angle for glass-air interface = arcsin(1/1.5) = 41.8 degree
so,a = 12tanC = 10.7cm?
I just guess...I am not sure about what the question is asking for...
Does it mean,assume the observer's position doesn't change,
he can see O before placing the circular label.And he couldn't see O after placing the circular label?
 

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  • #2


Show your attempt of solution, please. What equation is relevant? Draw the light ray from the spot towards the observer's eye. ehild
 
  • #3


jadelamlam said:

Homework Statement


as shown in the figure.

Homework Equations



The Attempt at a Solution

attachment.php?attachmentid=48388&d=1339823659.jpg



Hello jadelamlam.

You have posted threads on PF before, but apparently nobody has pointed out to you that the rules for posting a thread in the HomeWork section state that you must show some effort at arriving at a solution before we can help you.
"NOTE: You MUST show that you have attempted to answer your question in order to receive help. You MUST make use of the homework template, which automatically appears when a new topic is created in the homework help forums. Once your question or problem has been responded to, do not go back and delete (or edit) your original post."​

What have you tried ?

Where are you stuck ?
 
  • #4


Sorry,I have just edited my question.
 
  • #5


jadelamlam said:

The Attempt at a Solution


Critical angle for glass-air interface = arcsin(1/1.5) = 41.8 degree
so,a = 12tanC = 10.7cm?
I just guess...I am not sure about what the question is asking for...
Does it mean,assume the observer's position doesn't change,
he can see O before placing the circular label.And he couldn't see O after placing the circular label?

Your solution means that the light can not get out from the glass if that label is placed above the spot onto the surface. When a light ray strikes the surface at angle lees then the critical, the label is there. If it strikes the surface at angle greater than critical, it totally reflects. The observer can look from any direction, he can not see the spot. I think the problem means that solution. Otherwise the position of the observer should have been given.

ehild
 
  • #6


ehild said:
Your solution means that the light can not get out from the glass if that label is placed above the spot onto the surface. When a light ray strikes the surface at angle lees then the critical, the label is there. If it strikes the surface at angle greater than critical, it totally reflects. The observer can look from any direction, he can not see the spot. I think the problem means that solution. Otherwise the position of the observer should have been given.

ehild
Yes!

I agree with ehild regarding the interpretation of this problem !
 
  • #7


thx sooooooooo much :)
 

FAQ: Refraction - when can you see past the label?

What is refraction and how does it affect vision?

Refraction is the bending of light as it passes through different mediums, such as air and water. This bending of light is what allows us to see objects. When light enters our eyes, it is refracted by the cornea and lens before being focused on the retina, creating an image that our brain interprets as vision.

When can you see past the label on an object?

You can see past the label on an object when the light from the object is being refracted more by the medium it is passing through, compared to the light from the label. This can happen when the label is printed on a different material than the object or when there is a difference in the thickness of the object and the label.

Why do objects appear distorted when viewed through water?

When light passes through water, it is refracted at a different angle than when it passes through air. This causes the image of the object to be distorted, appearing closer or larger than it actually is. This is also why objects appear to be in a different place than they actually are when viewed through water.

Can refraction be controlled or manipulated?

Yes, refraction can be controlled and manipulated by using lenses and prisms. These optical instruments are designed to bend and focus light in specific ways, allowing us to correct vision problems, magnify objects, and even create illusions.

How does refraction impact the design of eyeglasses and contact lenses?

Refraction plays a crucial role in the design of eyeglasses and contact lenses. These corrective lenses are designed to refract light in a way that compensates for any vision problems, such as nearsightedness or farsightedness. By bending the light in a specific way, these lenses can help to improve vision and allow individuals to see clearly.

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