How Light Reflects from Surfaces

• Understand that light bounces back from shiny or smooth surfaces.
• Use the words incident ray, reflected ray, and normal at a basic level.
• Observe reflection in mirrors, steel plates, and calm water in Indian homes.
• Explain why reflection helps in daily life like rear-view mirrors and torches.

Level 1 - What is reflection?

When light falls on a surface and returns back, this is called reflection. We see our face in a mirror because light from our face reflects into our eyes. In many Indian homes, a steel thali also gives a weak reflection.

Level 2 - Smooth vs rough surfaces

Smooth surfaces like a mirror reflect light regularly, so image looks clear. Rough surfaces like a wall scatter light in many directions, so no clear image forms.

Level 3 - Simple ray idea

The incoming light is called the incident ray. The bounced light is the reflected ray. A line drawn at 90° to the surface is called the normal. For plane mirrors, angle of incidence equals angle of reflection.

Level 4 - Reflection in Indian context

At a cricket match under floodlights in Delhi, players see bright spots from helmets because of reflection. During Diwali, diyas in polished brass vessels look brighter due to reflected light. Reflection also helps drivers through rear-view mirrors and cyclists with reflective strips.

NCERT anchor: Looking Around 4, Ch 7 — From the Window; Ch 14 — Basva's Farm (observing sunlight and reflections around us)

Torch light on mirror

Step 1 - Shine a torch at a plane mirror on a table.
Step 2 - Mark the incoming direction with chalk as incident ray.
Step 3 - Observe outgoing direction and mark reflected ray.
Step 4 - Compare both angles from the normal; they match closely.
Answer: Light reflects with equal incoming and outgoing angles.

Choosing surface for clear reflection

Step 1 - Compare mirror, steel plate, and painted wall.
Step 2 - Look at your face in each surface.
Step 3 - Mirror shows clearest image, steel is blurred, wall none.
Step 4 - Link clarity with smoothness of surface.
Answer: Smoother surface gives clearer reflection.

• Name one smooth and one rough reflecting surface from your home.
• Why is your image clear in a mirror but not in a painted wall?
• In a rear-view mirror, does light reflect or refract?
• What is the line at 90° to surface called?
• Stretch: Try measuring angles using a protractor with a mirror and verify equal-angle reflection in at least two trials.

Revision tip: Remember: smooth surface -> regular reflection -> clear image; rough surface -> diffuse reflection -> no clear image.

Open the Practice tab for graded questions on How Light Reflects from Surfaces.