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Physics Optics
Asked 11 times in UPSC Prelims · first asked 1995 · last asked 2013
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Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this? 1) Dispersion 2) Refraction 3) Internal reflection
2013Sci & Tech
Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this? 1) Dispersion 2) Refraction 3) Internal reflection
Explanation
Rainbows are created when sunlight interacts with raindrops. The physical processes responsible for this phenomenon include dispersion, refraction, and internal reflection. Therefore, the correct option is (d), as all three of these phenomena play a role in the formation of rainbows.
In the figure shown above, OP1 and OP2 are two plane mirrors kept perpendicular to each other. S is the direction of a beam of light falling on the mirror OP1. The direction of the reflected beam of light from the mirror OP2 will be:
2011Sci & Tech
In the figure shown above, OP1 and OP2 are two plane mirrors kept perpendicular to each other. S is the direction of a beam of light falling on the mirror OP1. The direction of the reflected beam of light from the mirror OP2 will be:
Explanation
In the scenario depicted, two plane mirrors, OP1 and OP2, are positioned at right angles to each other. A beam of light is projected towards mirror OP1 in the direction of S. The light beam reflected from mirror OP2 will travel in a path that is opposite and parallel to the original direction S.
Consider the following statements: 1) If magenta and yellow coloured circles intersect, the intersected area will have red colour. 2) If cyan and magenta coloured circles intersect, the intersected area will have blue colour. Which of the statements given above is/are correct?
2007Sci & Tech
Consider the following statements: 1) If magenta and yellow coloured circles intersect, the intersected area will have red colour. 2) If cyan and magenta coloured circles intersect, the intersected area will have blue colour. Which of the statements given above is/are correct?
Explanation
In the given question, two statements are presented about the intersection of colored circles. The first statement suggests that if magenta and yellow circles intersect, the resulting area will be red. The second statement claims that when cyan and magenta circles intersect, the resulting area will be blue. The correct answer is option (c) - Both 1 and 2 are correct. It is important to note that the combination of red and blue colors produces magenta, while the combination of red and green colors results in yellow.
Consider the following statements: 1) Light of longer wavelength are scattered much more than the light of shorter wavelength. 2) The speed of visible light in water is 0.95 times the speed in vacuum. 3) Radio waves are produced by rapidly oscillating electrical currents. 4) To detect the overspeeding vehicles, police use the Doppler effect of reflected short radio waves. Which of these statements are correct?
2002Sci & Tech
Consider the following statements: 1) Light of longer wavelength are scattered much more than the light of shorter wavelength. 2) The speed of visible light in water is 0.95 times the speed in vacuum. 3) Radio waves are produced by rapidly oscillating electrical currents. 4) To detect the overspeeding vehicles, police use the Doppler effect of reflected short radio waves. Which of these statements are correct?
Explanation
Radio waves are generated by electrical currents that oscillate quickly. The police employ the Doppler effect of short radio waves reflected back to detect vehicles exceeding the speed limit.
Assertion (A): A stick is dipped in water in a slanting position. If observed sideways, the stick appears short and bent at the surface of water. Reason (R): A light coming from the stick undergoes scattering from water molecules giving the stick a short and bent appearance.
2001Sci & Tech
Assertion (A): A stick is dipped in water in a slanting position. If observed sideways, the stick appears short and bent at the surface of water. Reason (R): A light coming from the stick undergoes scattering from water molecules giving the stick a short and bent appearance.
Explanation
In this scenario, when a stick is placed in water at an angle and viewed from the side, it appears shortened and bent at the water's surface. The reason for this optical illusion is due to the phenomenon of light refraction by water molecules, not light scattering. Thus, the assertion that the stick looks short and bent in water is true, but the explanation given related to light scattering is false.
Assertion (A): Small glass beads fixed on traffic signals glow brightly when light falls upon them. Reason (R): Light is totally reflected when the angle of incidence exceeds a certain critical value and light travelling in a denser medium is reflected from a rarer medium.
2000Sci & Tech
Assertion (A): Small glass beads fixed on traffic signals glow brightly when light falls upon them. Reason (R): Light is totally reflected when the angle of incidence exceeds a certain critical value and light travelling in a denser medium is reflected from a rarer medium.
Explanation
In this scenario, small glass beads on traffic signals shine brightly when light shines on them. This is because light gets completely reflected when its angle of incidence surpasses a specific critical value, and light traveling from a denser medium reflects off a rarer medium. The correct option is that both statements are true, and the second statement is the correct explanation for the first statement.
Consider the following statements: 1) If a person looks at a coin which is in a bucket of water, the coin will appear to be closer than it really is. 2) If a person under water looks at a coin above the water surface, the coin will appear to be at a higher level than it really is. Which of the above statements is/are correct?
1999Sci & Tech
Consider the following statements: 1) If a person looks at a coin which is in a bucket of water, the coin will appear to be closer than it really is. 2) If a person under water looks at a coin above the water surface, the coin will appear to be at a higher level than it really is. Which of the above statements is/are correct?
Explanation
When a person views a coin in a bucket of water, the coin appears closer than its actual position due to refraction of light from denser water to rarer air. Conversely, when a person underwater looks at a coin above the water surface, refraction occurs in the opposite direction, making the coin seem higher than it really is.
When a mirror is rotated by an angle θ, the reflected ray will rotate by:
1996Sci & Tech
When a mirror is rotated by an angle θ, the reflected ray will rotate by:
Explanation
In this scenario, when a mirror is rotated by an angle θ, the reflected ray will rotate by an angle of 2θ. This means that the reflected ray will rotate twice as much as the angle by which the mirror is rotated.
Total internal reflection can take place when light travels from:
1996Sci & Tech
Total internal reflection can take place when light travels from:
Explanation
Total internal reflection occurs in optics when a ray of light hits the boundary of a medium at an angle greater than a specific critical angle in relation to the surface's normal.
Assertion (A): A diamond sparkles more than a glass imitation cut to the same shape. Reason (R): The refractive index of diamond is less than that of glass.
1995Sci & Tech
Assertion (A): A diamond sparkles more than a glass imitation cut to the same shape. Reason (R): The refractive index of diamond is less than that of glass.
Explanation
In this physics concept, a diamond sparkles more than a glass imitation cut to the same shape because of a difference in refractive index. The refractive index of diamond is actually higher than that of glass. This phenomenon is due to total internal reflection of light, which occurs based on the critical angle of light incidence in a material medium at its interface with air.
An air bubble in water will act like a:
1995Sci & Tech
An air bubble in water will act like a:
Explanation
When an air bubble is submerged in water, it behaves like a concave lens. This is because the refractive index of air is lower than that of water, causing the light to diverge when passing through the bubble.