Optical Element

Focal Length (f) 100 mm

Object Distance (u) 200 mm

Object Height (h) 60 mm

Ray Visualization

Parallel Ray Central Ray Focal Ray

Image Distance (v)

Magnification (m)

Nature

🖱️ Drag object or focus points to adjust

CBSE Class 12 Physics

Ray Optics & Optical Instruments

Complete guide to spherical lenses, mirrors, and the principles of image formation

🎯 How to Use This Virtual Lab

Follow these steps to conduct your experiment and calculate focal lengths accurately:

Select Your Optical Device

Choose between convex lens, concave lens, concave mirror, or convex mirror from the dropdown menu at the top right.

Adjust Parameters

Use the sliders to change focal length (f), object distance (u), and object height (h). Watch the real-time ray diagram update automatically.

Observe Ray Paths

Enable/disable different rays (parallel, central, focal) to understand how light behaves through lenses and mirrors. The image formation is shown instantly.

Record Observations

Click "Record Reading" to save your current measurements. The image distance (v) and magnification (m) are calculated automatically.

Analyze Data

Switch to the Data tab to view your recorded readings in a table and graph. Calculate average focal length and verify the lens/mirror formula.

📖 Essential Terminology ▼

Optical Centre (C)

The central point of a lens through which light rays pass without deviation. It serves as the reference point (origin) for measurements in the new Cartesian sign convention.

Pole (P)

The geometric center of a spherical mirror's reflecting surface. For mirrors, the pole acts as the origin in sign convention calculations.

Principal Focus (F)

The point where parallel rays converge (converging systems) or appear to diverge from (diverging systems) after reflection or refraction.

Focal Length (f)

The distance between the optical centre/pole and the principal focus. Positive for converging systems, negative for diverging systems.

Object Distance (u)

The distance of the object from the optical centre or pole. Always measured as negative in the new Cartesian sign convention.

Image Distance (v)

The distance of the image from the optical centre or pole. Positive for real images, negative for virtual images (lenses). Opposite for mirrors.

📐 New Cartesian Sign Convention ▼

Essential Rules for Accurate Calculations

1. Origin Point

• For lenses: Optical Centre (C) is the origin

• For mirrors: Pole (P) is the origin

2. Direction of Light

• Light travels from left to right (positive x-direction)

• All distances are measured from the origin

3. Sign Rules

Horizontal (x-axis):

• Distances measured in direction of incident light: Positive (+)

• Distances measured against incident light: Negative (−)

Vertical (y-axis):

• Heights measured upward: Positive (+)

• Heights measured downward: Negative (−)

💡 Important Notes

• Object distance (u) is always negative since objects are placed against the direction of light

• Real images: v is positive for lenses, negative for mirrors

• Virtual images: v is negative for lenses, positive for mirrors

• Inverted images have negative height

• Erect images have positive height

🧮 Lens & Mirror Formulas ▼

Lens Formula

1/f = 1/v - 1/u

Used for both convex and concave lenses

Mirror Formula

1/f = 1/v + 1/u

Used for both concave and convex mirrors

Magnification Formula

m = v/u = h'/h

where h' is image height and h is object height
m > 1: Magnified | m < 1: Diminished
m > 0: Erect | m < 0: Inverted

Power of a Lens (P)

The power of a lens is its ability to converge or diverge light rays. It is defined as the reciprocal of the focal length in meters.

P = 1/f(m)

Unit: Dioptre (D)
1 D = 1 m⁻¹

Convex lens: Positive power
Concave lens: Negative power

🔬 Image Formation Rules ▼

Convex Lens

Object Position	Image Position	Nature & Size
At infinity	At F	Real, inverted, highly diminished
Beyond 2F	Between F and 2F	Real, inverted, diminished
At 2F	At 2F (other side)	Real, inverted, same size
Between F and 2F	Beyond 2F	Real, inverted, magnified
At F	At infinity	Real, inverted, highly magnified
Between F and C	Same side as object	Virtual, erect, magnified

Concave Mirror

Object Position	Image Position	Nature & Size
At infinity	At F	Real, inverted, highly diminished
Beyond C	Between F and C	Real, inverted, diminished
At C	At C	Real, inverted, same size
Between F and C	Beyond C	Real, inverted, magnified
Between F and P	Behind mirror	Virtual, erect, magnified

💡 Real-World Applications ▼

🔬 Microscopes

Compound microscopes use two convex lenses (objective and eyepiece) to produce highly magnified images of tiny specimens like cells and bacteria.

🔭 Telescopes

Refracting telescopes use convex lenses to gather and magnify light from distant celestial objects, allowing us to observe stars and planets.

📷 Cameras

Camera lenses use convex lenses to focus light and form real, inverted images on the sensor or film, capturing photographs.

👓 Eyeglasses

Convex lenses correct hypermetropia (farsightedness) while concave lenses correct myopia (nearsightedness) by adjusting focal length.

🚗 Vehicle Mirrors

Convex mirrors are used as rear-view and side-view mirrors in vehicles because they provide a wider field of view with erect, diminished images.

🦷 Dental Mirrors

Concave mirrors are used by dentists to get magnified views of teeth when held close, utilizing virtual, erect, and enlarged images.

☀️ Solar Concentrators

Concave mirrors focus sunlight to a single point (focus), generating intense heat for solar cookers and power generation systems.

💡 Headlights

Vehicle headlights use concave mirrors with the bulb at the focus to produce parallel beams of light for effective illumination.

Experimental Observations

#	u (cm)	v (cm)	f (calc)	Error %
No observations recorded yet. Switch to Simulation and click "Record Reading" to add data.

Ray Optics & Optical Instruments

🎯 How to Use This Virtual Lab

Select Your Optical Device

Adjust Parameters

Observe Ray Paths

Record Observations

Analyze Data

Optical Centre (C)

Pole (P)

Principal Focus (F)

Focal Length (f)

Object Distance (u)

Image Distance (v)

Essential Rules for Accurate Calculations

1. Origin Point

2. Direction of Light

3. Sign Rules

💡 Important Notes

Lens Formula

Mirror Formula

Magnification Formula

Power of a Lens (P)

Convex Lens

Concave Mirror

🔬 Microscopes

🔭 Telescopes

📷 Cameras

👓 Eyeglasses

🚗 Vehicle Mirrors

🦷 Dental Mirrors

☀️ Solar Concentrators

💡 Headlights

Experimental Observations

Graph: 1/v vs 1/u