When light travels from a medium with higher refractive index to a medium with lower refractive index, there is a critical angle after which all the light is reflected (so, there is no refraction).
The value of this critical angle can be derived by Snell's law, and it is equal to

where n2 is the refractive index of the second medium and n1 is the refractive index of the first medium.
In our problem, n1=1.47 and n2=1.33, so the critical angle is
Answer:
They contain iron.
Explanation:
Iron is made of metal and magnets attract to metal Iron.
1. Physical size of Russia compared to other countries, despite a lack of visible borders from space.
2. Part of Russia's outline would likely be obscured by the various clouds and objects in the stratosphere; this would allow the astronaut to view potential cloud and weather patterns on earth.
3. An astronaut could see outlines of Russia's geography such as mountain ranges.
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Here is the energy that is left after the quantity of energy is transformed: 750 j of electrical energy is changed into 400 j of kinetic or mechanical energy, which is then turned into 0.32 j of efficient energy.
To run the fan, electrical energy is utilized.
Here, under the specified circumstances, 750 J of electrical energy is utilized to operate the fan, which is transformed into 400 J of kinetic energy. As a result, 350 J of energy is wasted due to various frictional and resistive losses.
Therefore, we may conclude that only 400 J of the 750 J available energy is used to power the fan, with the remaining energy being wasted as a result of friction.
Additionally, we can state that this fan's effectiveness will be
n = Useful ÷ Total
n = 400 ÷ 750
n = 8 ÷ 25
n = 0.32
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Given data
*The given mass of the pendulum is m = 3 kg
*The given height is h = 0.3 m
The formula for the maximum speed of the pendulum is given as
![v_{\max }=\sqrt[]{2gh}](https://tex.z-dn.net/?f=v_%7B%5Cmax%20%7D%3D%5Csqrt%5B%5D%7B2gh%7D)
*Here g is the acceleration due to the gravity
Substitute the values in the above expression as
![\begin{gathered} v_{\max }=\sqrt[]{2\times9.8\times0.3} \\ =2.42\text{ m/s} \end{gathered}](https://tex.z-dn.net/?f=%5Cbegin%7Bgathered%7D%20v_%7B%5Cmax%20%7D%3D%5Csqrt%5B%5D%7B2%5Ctimes9.8%5Ctimes0.3%7D%20%5C%5C%20%3D2.42%5Ctext%7B%20m%2Fs%7D%20%5Cend%7Bgathered%7D)
Hence, the maximum speed of the pendulum is 2.42 m/s