Why Was My Answer of 63 cm for the Focal Length of a Converging Lens Incorrect?

Thread starter syllll_213
Start date Apr 15, 2025

Apr 15, 2025

syllll_213

Homework Statement: An object is in a distance of 14 cm from a converging lens. The lens produces a virtual image at a distance 18 cm from the object.

What is the focal length of the lens (in cm).

Relevant Equations: 1/f = 1/di + 1/do

I attempted and keyed in the answer as 63 but I was graded wrong. What am I missing?

Physics news on Phys.org

Apr 15, 2025

haruspex

Science Advisor

Homework Helper

Insights Author

Gold Member

2024 Award

syllll_213 said:

Homework Statement: An object is in a distance of 14 cm from a converging lens. The lens produces a virtual image at a distance 18 cm from the object.

Thread 'Rolling without slipping on a curved surface'

Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .

View full post »

Thread 'Voltmeter readings for this circuit with switches'

TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...

View full post »

Thread 'Power of a thin lens in a medium is 1/fₘ or μₘ/fₘ ?'

Here is what I tried This question was actually asked in one of our engineering entrances. The answer was 1D. My teachers say that we have to use μₘ/fₘ to get to this answer. I cannot understand why. I'll be really glad if you could tell me the exact definition of power (numerically) that works in all scenarios.

View full post »