Answer
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Hint: Critical angle is the angle of incidence, where the angle of refraction equals 90 degrees. We can see that the refracted light rays move away from the normal line depending on the angle of incidence. For different angles of incidence, the angle of refraction also differs.
Complete step-by-step solution
When the angle of incidence of the light ray is greater than the critical angle, no refraction takes place. Instead, all the light gets reflected back into the denser medium. This is called total internal reflection. The critical angle occurs for the angle of incidence, where the angle of refraction is 90°.
From the 1st figure, we can see that the light is traveling through the water towards the air-water interface. Here, water is denser than air. The light rays will emerge out of the denser medium to the rarer medium and the angle of refraction is less than 90 degrees.
From the second figure, we can see that the angle of incidence in water reaches a particular value, the refracted ray lies along the boundary, with an angle of refraction of 90-degrees. This incident angle is called the critical angle. It is the largest angle of incidence for which refraction of light rays can occur.
From the third figure, we can see that, for any angle of incidence greater than the critical angle, the light will reflect back to the denser medium. It is called total internal reflection.
Therefore, the answer is option A true.
Note: Beyond the critical angle, light rays are always reflected. Optical fiber cables work based on this principle. And the brilliance of diamonds is due to total internal reflection. When light passes from rarer to a denser medium, total internal reflection does not occur.
Complete step-by-step solution
When the angle of incidence of the light ray is greater than the critical angle, no refraction takes place. Instead, all the light gets reflected back into the denser medium. This is called total internal reflection. The critical angle occurs for the angle of incidence, where the angle of refraction is 90°.
From the 1st figure, we can see that the light is traveling through the water towards the air-water interface. Here, water is denser than air. The light rays will emerge out of the denser medium to the rarer medium and the angle of refraction is less than 90 degrees.
From the second figure, we can see that the angle of incidence in water reaches a particular value, the refracted ray lies along the boundary, with an angle of refraction of 90-degrees. This incident angle is called the critical angle. It is the largest angle of incidence for which refraction of light rays can occur.
From the third figure, we can see that, for any angle of incidence greater than the critical angle, the light will reflect back to the denser medium. It is called total internal reflection.
Therefore, the answer is option A true.
Note: Beyond the critical angle, light rays are always reflected. Optical fiber cables work based on this principle. And the brilliance of diamonds is due to total internal reflection. When light passes from rarer to a denser medium, total internal reflection does not occur.