The reddish appearance of the sun at sunrise and sunset is due to:
1. the scattering of light.
2. the polarisation of light.
3. the colour of the sun.
4. the colour of the sky.
Subtopic:  Total Internal Reflection |
 89%
Level 1: 80%+
NEET - 2013
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If the critical angle for total internal reflection from a medium to vacuum is \(45^{\circ}\), the velocity of light in the medium is: 

1. \(1.5\times10^{8}~\text{m/s}\) 2. \(\dfrac{3}{\sqrt{2}}\times10^{8}~\text{m/s}\)
3. \(\sqrt{2}\times10^{8}~\text{m/s}\) 4. \(3\times10^{8}~\text{m/s}\)

Subtopic:  Total Internal Reflection |
 83%
Level 1: 80%+
NEET - 2020
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Which set of colours would be observed in the air under the conditions depicted in the figure?
1. yellow, orange, and red 2. blue, green, and yellow
3. orange, red, and violet 4. all of the above
Subtopic:  Total Internal Reflection |
 76%
Level 2: 60%+
NEET - 2023
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An empty cylindrical beaker whose height is equal to its diameter is kept on a table. An observer's eye\((E)\) looking towards \(S\) (line of sight: \(ES\)) can see the point \(Q\) on the lower right. The angle of view, \(\theta,\) is the angle the line of sight \(ES,\) makes with the vertical \(RS\)-extended. A transparent liquid is now slowly poured into the beaker. As the liquid level rises in the beaker, the line of sight has to be continually adjusted (by increasing angle \(\theta\)) in order to keep \(Q\) visible. When the liquid fills the beaker to the brim, \(Q\) can no more be seen by adjusting the line of sight \(ES. \) The minimum refractive index of the liquid should be:
1. \(\dfrac32\) 2. \(2\)
3. \(\sqrt{\dfrac32} \) 4. \(\sqrt2\)
Subtopic:  Total Internal Reflection |
Level 3: 35%-60%
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