Key relationship
First q₁=f₁d/(d−f₁); second signed d₂=L−q₁;1/f₂=1/d₂+1/q₂.
Physics · Practical apparatus
Concave lens in a converging beam
A concave lens can yield a real final image when its incident beam is already converging sufficiently. The virtual-object distance must be signed, otherwise the focal calculation is wrong.
Open the interactive experiment →Concave lens in a converging beam
ஏற்கனவே குவியும் கதிர்களில் குழி லென்சுக்கும் உண்மை இறுதிப் பிம்பம் கிடைக்கலாம். மெய்நிகர் பொருளின் தொலைவு குறியுடன் பயன்படுத்த வேண்டும்.
Key notes, relationships and model limits
Practical tip
A concave lens can yield a real final image when its incident beam is already converging sufficiently. The virtual-object distance must be signed, otherwise the focal calculation is wrong.
Common trap
A concave lens is not restricted to virtual images when the incident object itself is virtual.
Model limits
Separated thin lenses; negative d₂ is a virtual object in a converging beam. If a lens or object plane makes a denominator zero, a finite screen image is unavailable.
What you will learn
Use a convex lens to measure a diverging element.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
First focus60 cm and lens position40 gives d₂−20 cm; f₂−40 gives q₂40 cm.
Why this matters
The model connects concave lens in a converging beam with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
The second lens virtual-object distance is?
- Always positive
- Negative in this positive-real-distance convention
- Always zero
Read the explanation
Its would-be object lies on the outgoing side.
Course connection: Virtual apparatus preparation. Check exact board/exam membership in the syllabus sources. Physical practical work remains necessary.