Read Modified Lenses: Follow Refraction, Reflection, Refraction
This short read prepares one exact NSEP pattern: lens maker and a silvered lens. Identify the physical condition before calculating.
Lens Maker and a Silvered Lens is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Start with the physical model
Read the configuration once, state the conserved quantity or governing law, and mark any changing geometry, sign convention or limiting condition.
Build the relation
With µ=1.5, R1=+20 cm and R2=-60 cm, 1/f=0.5(1/20+1/60)=1/30, so f=30 cm: A. When the R2 surface is silvered, refraction through the lens followed by reflection and a second refraction combines to give an effective concave-mirror focal length of 10 cm: B. Filling only the image space with liquid of µ=5/3 does not make the total system diverging, so C is false. With water (µ=4/3) on the image side, applying refraction at the two spherical surfaces gives a parallel-ray focus 48 cm behind the lens: D. Correct A,B,D. IOQP 2021-22 Part I - Code 61 - Detailed Solutions.
Check before selecting
Check units, sign and one limiting case. A valid result must still fit the original geometry and stated constraint.
OlympIQ exam lens
- ✓Name the governing law before using a formula.
- ✓Keep the stated geometry and direction information explicit.
- ✓Use one unit or limiting-case check.
A silvered surface makes light pass through the lens twice; do not use the one-pass lens formula alone.
Ready to try the pattern?
100% coverage across the linked question.
Practise the linked question