Steps to Draw convex & concave lens .for see...Wave chapter for class 10

Here is a simple, step-by-step guide to drawing both types of lenses using basic geometry tools (a compass and a ruler).

1. How to Draw a Convex Lens

A convex lens is thicker in the middle and thinner at the edges. It is formed by the intersection of two spherical surfaces.

Draw the Principal Axis: Use a ruler to draw a long horizontal line. Mark a point O in the center; this is the Optical Center.

Mark the Focus and Center of Curvature: Measure equal distances on both sides of O. Mark points F1​ and 2F1​ (on the left) and F2​ and 2F2​ (on the right). (e.g., O to F=3 cm, O to 2F=6 cm).

Draw the Arcs:

Place your compass needle on 2F1​ and open it to reach slightly past the O point. Draw a light arc.

Without changing the compass width, place the needle on 2F2​ and draw a second arc that intersects the first.

Connect the Tips: The area where the two arcs overlap forms your convex lens. Draw a vertical dashed line through the center (O) to represent the aperture.

2. How to Draw a Concave Lens

A concave lens is thinner in the middle and thicker at the edges. It "caves" inward.

Draw the Principal Axis: Just like the convex lens, draw a horizontal line and mark the Optical Center (O).

Mark the Points: Mark F1​,2F1​,F2​, and 2F2​ at equal intervals.

Draw Two Curved Brackets: * Place your compass needle at a point further out on the axis (beyond 2F).

Draw an arc that curves inward toward the center.

Repeat this on the opposite side so the two curves face away from each other (like back-to-back parentheses: )( ).

Close the Lens: Use straight horizontal lines to connect the top ends of the arcs and the bottom ends of the arcs.

Aperture: Draw a vertical dashed line through the center (O).

Pro-Tips for Class 10 Ray Diagrams

The 1:2 Ratio: Always make the distance from O to 2F exactly double the distance from O to F. This ensures your light rays meet exactly where they are supposed to.

Thin Lens Approximation: In Class 10, we assume lenses are very thin. When drawing light rays, always draw them traveling to the vertical center line (aperture) before they bend (refract).

Arrows: Always include arrows on your ray lines to show the direction of light.

Would you like me to explain the rules for refraction (how the light rays actually bend) for these lenses next?