High yield5 mapped NDA questions
Build the idea
Ray optics is best learned visually. Trace principal rays first, then apply the sign convention and formula. NDA asks image position, magnification, total internal reflection and everyday optical devices.
Concept
Light travels in straight lines and can be reflected (bouncing off a surface) or refracted (bending when passing between media). Mirrors and lenses form images used in many devices.
Concave mirrors and convex lenses can converge light; convex mirrors and concave lenses diverge it.
Key Points & Formulas
- Law of reflection: angle of incidence = angle of reflection.
- Refraction: light bends towards the normal entering a denser medium.
- Concave mirror: converging (used in headlights, shaving mirrors).
- Dispersion: a prism splits white light into seven colours.
Worked Example
Q. Which mirror is used as a vehicle's rear-view mirror and why?
A convex mirror is used.
It always forms an erect, diminished image and gives a wider field of view.
This lets the driver see more of the traffic behind.