Physics · Practical apparatus

Concave-mirror u-v bench

Move the screen until its distance agrees with the calculated real-image position. Record object and image distances, then estimate focal length. An object inside focus yields no sharp screen image.

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Concave-mirror u-v bench

திரையை உண்மை பிம்ப இடத்தில் வைத்து u-v வாசிப்புகளிலிருந்து குவியத் தொலைவைக் கணக்கிடவும்.

Key notes, relationships and model limits

Key relationship

1/f=1/d+1/q; at a sharp real image, f=dq/(d+q).

Practical tip

Move the screen until its distance agrees with the calculated real-image position. Record object and image distances, then estimate focal length. An object inside focus yields no sharp screen image.

Common trap

A low sharpness reading may indicate virtual imaging, not just a badly positioned screen.

Model limits

Ideal concave paraxial mirror; positive bench distances. Sharpness is a normalized defocus guide, not measured optical resolution. Virtual images cannot be caught on the screen.

What you will learn

Obtain a focal estimate from a real u-v arrangement.

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

d60 cm,q30 cm gives f20 cm.

Why this matters

The model connects concave-mirror u-v bench with an observable reading. Check the equation and assumptions before applying it.

Before you start

SI units · algebra · graph reading

Check your understanding

A virtual concave-mirror image can be projected directly on the screen?

Always
No
Only if the screen is opaque

Read the explanation

Virtual rays do not converge at a screen behind their extensions.

Course connection: Virtual apparatus preparation. Check exact board/exam membership in the syllabus sources. Physical practical work remains necessary.