Wednesday, August 3, 2011

Common Misconceptions on Critical Angle and Main Take away for the Day

Please answer the question below in the comment box. 

1) How would critical angle of a rectangle glass block change when we
    a) increase the thickness of the glass block;
    b) increase the angle of incidence of the ray exiting the glass block;
    c) change the material of the rectangle glass block to another of higher refractive index?

2) What are the main concept(s) learnt for today's lesson? Give at least 3 of them.

20 comments:

  1. 2) What are the main concept(s) learnt for today's lesson? Give at least 3 of them.

    1. Refraction and reflection takes place when light passes through transparent objects.

    2. Light does not go through reflection or refraction when it is pointed 90º to the surface of the object.

    3. The critical angle is when the weak reflected ray is 180º to the flat surface of the object.

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  2. a) It will not change
    b) The critical angle will not change.
    c) The optical density of the glass changes so the critical angle changes

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  3. 1a) The critical angle would not change.

    1b) The critical angle would not change.

    1c) By changing the material of the rectangle glass block to another of a higher refractive index, the critical angle of the glass block would be decrease.

    2) The main concepts that I have taken away from the chapter of refraction is that total internal reflection occurs when the angle of incidence is greater than the critical angle, the light ray would bend away from the normal when traveling from a denser to less dense place and that when the ray is perpendicular to the surface, no refraction and reflection will occur.

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  4. 1) a) It remains unchanged
    b) It remains unchanged
    c) The critical angle will decrease

    2) - The critical angle can only be changed if the refractive index of the medium is changed.
    - Critical angle is the angle of incidence when the angle of refraction is 90º
    - Total internal reflection only occur when the light travel from optically denser medium to less dense medium and the angle of incidence is more than the critical angle

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  5. if the angle of incidence is bigger than the critical angle and it is from denser to less denser medium, total reflection will occ

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  6. 1a) The critical angle would not change.
    1b) The critical angle would not change.
    1c) The optical density of the medium changes, hence, the critical angle also changes.

    2)

    - The ray will bend towards the normal line when it is travelling through a denser medium to a lesser dense medium. ( refraction )

    - criteria for total internal reflection would be that the angle of incidence must be greater than the critical angle, and the ray has to travel through a denser to less densed medium

    - total internal reflection occurs on the surface of the medium.

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  7. 1a) The critical angle will not change.
    1b) The critical angle will not change.
    1c) When the material is changed, the refractive index will change and therefore the critical angle will change too.

    2) When angle i=40 for the glass block, angle r=90. Angle of incidence must be greater than critical angle for total internal refraction to occur. The ray must also pass through from a denser medium to a less dense medium.

    When a ray travels from a denser medium to a less dense medium, the refracted ray bends away from the normal. When a ray travels from a less dense medium to a denser medium, the refracted ray bends towards the normal.

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  8. 1) (a) When we increase the thickness of the glass block, the thickness of the glass block remains the same.

    (b) When the angle of incidence is increased the critical angle will remain the same.

    (c) The density of the glass will change.

    2) THe main concepts I have learnt is that light does not go through the process of refraction or reflection when 90 degrees perpendicular to the surface of the object.

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  11. 1) How would critical angle of a rectangle glass block change when we
    a) increase the thickness of the glass block;
    b) increase the angle of incidence of the ray exiting the glass block;
    c) change the material of the rectangle glass block to another of higher refractive index?

    a) The critical angle does not change.
    b) The critical angle does not change.
    c) The critical angle increases

    2) What are the main concept(s) learnt for today's lesson? Give at least 3 of them.
    ~ To have total Internal Refraction, the angle of incidence must be greater than the critical angle and the ray must be moving from a denser to a less dense medium.
    ~ The ray will bend away from the normal when moving from denser to less dense.
    ~ The ray will bend towards the normal when moving from less dense to denser.
    ~ Higher Refractive Index = Higher Optical Density
    ~ Critical angle is the incidence angle when refracted ray is perpendicular to the normal.
    ~ When the angle of refraction increases when the angle of incidence increases.
    ~ When the ray is perpendicular to the surface, the reflected ray would be reflected back to the light box and the refraction ray passes through without bending.
    ~ There is no refraction when there is total internal reflection.
    ~ Ray would not bend if traveling through two similar medium with the same refractive index.
    ~ Check the movement of the ray at every boundary (angle of incidence + critical angle, less dense to denser, denser to less dense, label direction of ray, check the angles, write working.)

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  12. 1) How would critical angle of a rectangle glass block change when we
    a) increase the thickness of the glass block;

    There would be no change. (same as putting two of the same medium together)

    b) increase the angle of incidence of the ray exiting the glass block;

    There would be no change.

    c) change the material of the rectangle glass block to another of higher refractive index?

    The critical angle would increase.

    2) What are the main concept(s) learnt for today's lesson? Give at least 3 of them.

    -For total internal reflection to occur, i > c , denser to less dense.

    -When travelling from a denser to less dense medium, the ray would bend away from the normal line.

    -When travelling from a less dense to denser medium, the ray would bend towards the normal line.

    -Total internal reflection would not occur when the conditions are not met and refraction would occur.

    - Critical angle is the angle of incidence when the angle of refraction is 90º.

    - To make the ray pass through a medium without bending, the ray must be perpendicular to the surface.

    - When drawing diagrams, remember to check every time the ray hits the edge of the diagram, label every angle, and do the workings at the side.

    - There is NO refraction when there is total internal reflection.

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  13. 1) How would critical angle of a rectangle glass block change when we
    a) increase the thickness of the glass block;

    The critical angle would would not change.

    b) increase the angle of incidence of the ray exiting the glass block;

    The critical angle would would not change.

    c) change the material of the rectangle glass block to another of higher refractive index?

    The critical angle will increase.

    2) What are the main concept(s) learnt for today's lesson? Give at least 3 of them.

    Between 2 media, the sin of the angle of incidence to the sin of the angle of refraction, is a constant.

    When a light ray transits of a medium of lower density to a medium of higher density, it bends towards the normal.

    When a light ray transits of a medium of higher density to a medium of lower density , it bends away from the normal

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  14. 1) How would critical angle of a rectangle glass block change when we
    a) increase the thickness of the glass block;
    the critical angle remains the same
    b) increase the angle of incidence of the ray exiting the glass block;
    the critical angle will increase
    c) change the material of the rectangle glass block to another of higher refractive index?
    critical angle will decrease
    2) What are the main concept(s) learnt for today's lesson? Give at least 3 of them.

    1) Total Internal Refraction will only occur when the angle of incidence is more than critical angle and when path of ray goe sfrom a denser to less dense medium

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  15. 1) How would critical angle of a rectangle glass block change when we
    a) increase the thickness of the glass block
    The critical angle will not change

    b) increase the angle of incidence of the ray exiting the glass block
    The critical angle will not change.

    c) change the material of the rectangle glass block to another of higher refractive index?
    The critical angle will decrease

    2) What are the main concept(s) learnt for today's lesson? Give at least 3 of them.
    - Light pass through the mediums through a straight line when it is perpendicular to the mediums
    - Critical angle is the angle of incidence when the angle of refraction is 90˚
    - Total internal reflection occurs when the angle of incidence is greater than the critical angle

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  16. Increasing thickness of the glass block would not change the critical angle as the angle of refraction would not change. With a higher refractive index, the material and optical density of the medium remain the same, and thus refracts light the same way and thus does not change the critical angle. However changing the refractive index of a medium would change the the critical angle as the equation ---> sin^-1(1/n) The greater the index of refraction, the lower the critical angle. This is because it takes a lower angle of incidence to reach a critical angle as the light refract more in a medium with higher index of refraction

    THUS, only c) would change the critical angle... :D

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  18. 1a) Increasing the thickness of the glass block will not increase or decrease the critical angle.

    1b) Increasing the Angle of Incidence of the ray exiting the glass block will not increase or decrease the critical angle.

    1c) By changing the material of the rectangle glass block to another of higher refractive index, the critical angle will decrease.

    2i) For total internal reflection to occur, it must be in a more optically dense medium and travel a less optical dense medium.

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  19. Q1.
    a) The critical angle will remain the same .
    b) The critical angle will remain the same .
    c) As the refractive index is changed, the critical angle change too.

    Q2.

    a) The critical angle is the angle of incidence when the angle of refraction is 90 degrees .
    b) Total internal reflection occurs when a ray of light is incident upon a boundary with an optically rarer medium (one that makes it speed up) and the angle of incidence is greater than the critical angle.

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  20. 1) How would critical angle of a rectangle glass block change when we
    a) increase the thickness of the glass block;
    The critical angle will remain the same
    b) increase the angle of incidence of the ray exiting the glass block;
    The critical angle will remain the same
    c) change the material of the rectangle glass block to another of higher refractive index? The critical angle will remain the same even though the block is in a higher refractive index .

    ReplyDelete