Virtual Science Lab — Experiment 1

Determination of the Focal Length of a Convex Lens

Aim: To determine the focal length of a given thin convex lens by focusing the real, inverted image of an object (either a distant tree or an illuminated bench object) onto a white screen.

Interactive Setup

Graduated Optical Bench (0 – 100 cm)

Blurred Image (5.0 cm off)

Presets:

View on Physical Screen

🌳Inverted Real Image

Blur: 3.8pxFocus position: 50.0 cm

1. Object Position (O):Distant (∞)u ≈ ∞

Object is placed far away (incident rays are parallel).

2. Convex Lens Position (L):30 cm

3. Move Screen to Focus (S):45 cm (v = 15 cm)

Formula: f = v

u = ∞v = 15 cm

Lab Ledger

Observation & Calculation Table

Trial #	Object Pos (O)	Lens Pos (L)	Screen Pos (S)	u = L - O	v = S - L	Focal Length (f)	Status
No trials recorded yet. Position object and lens, move screen until image is sharp, then click Record Observation.

Oral Viva Examination

Concept Verification & Viva Questions

1. What is the nature of the image formed by a convex lens for a distant object?

2. Why is a distant tree or building selected instead of a nearby candle flame?

3. If the lower half of the convex lens is covered with black paper, what happens to the image?