True orFalse? Three light rays start outfrom a candle flame at the same time. To

Question

True orFalse?

Three light rays start outfrom a candle flame at the same time. To the right of thecandle

there is a lens, and tothe right of the lens there is a screen. Ray A goes through theedge

of the lens. Ray B goesthrough the center of the lens. Ray C goes through an

intermediate part of thelens. All three rays are focused on the screen. Ray B arrivesat

the screen first becauseit travels the shortest path. (Hint: draw the candle, lens,and

screen as well as thethree rays.)

If this statementis true, prove it. If false, show why it isfalse.

Explanation / Answer

   False    Although three rays travel differentdistances in reaching the screen, time taken is same. This isbecause there velocity in glass is less than velocity in air. Sothe rays that travels most part in air ( passing through thinnerpart of lens) travels at faster average velocity than the ray thattravels greater distance in lens. The effect exactly compensatesfor difference in path lens. This is in accordance with Fermat'sprinciple.    Although three rays travel differentdistances in reaching the screen, time taken is same. This isbecause there velocity in glass is less than velocity in air. Sothe rays that travels most part in air ( passing through thinnerpart of lens) travels at faster average velocity than the ray thattravels greater distance in lens. The effect exactly compensatesfor difference in path lens. This is in accordance with Fermat'sprinciple.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.