Light — Class 7 Science NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 7 Science chapter "Light" — 8 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 7 Science chapter "Light" — 8 important questions with detailed answers for CBSE board exam preparation.

By Syllab.in · Updated Jun 14, 2026

Key Questions Covered:

Define light. How does it travel?
What are plane mirrors? Explain the laws of reflection.
What is the difference between reflection and refraction?
What is a lens? Explain convex and concave lenses.
Define angle of incidence and angle of refraction.
What are the properties of light reflected by a plane mirror?
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
Define light. How does it travel?	✓ Solved
What are plane mirrors? Explain the laws of reflection.	✓ Solved
What is the difference between reflection and refraction?	✓ Solved
What is a lens? Explain convex and concave lenses.	✓ Solved
Define angle of incidence and angle of refraction.	✓ Solved
What are the properties of light reflected by a plane mir…	✓ Solved

Showing 6 of 8 questions

Q1: Define light. How does it travel?

Light: form of energy that enables us to see objects. It is electromagnetic radiation visible to human eye (wavelength 380-700 nm). Light travels in straight lines (rectilinear propagation) with speed 3 × 10⁸ m/s in vacuum. Speed of light = c = 3 × 10⁸ m/s. Light travels slower in other media (water, glass) than in vacuum.

Q2: What are plane mirrors? Explain the laws of reflection.

Plane mirror: flat, smooth reflective surface. Laws of reflection: 1. Angle of incidence = Angle of reflection (both measured from normal) 2. Incident ray, reflected ray, and normal all lie in same plane 3. Rays reflect on smooth surfaces following these laws Image in plane mirror: virtual, erect, same size as object, laterally inverted, same distance behind mirror as object is in front.

Q3: What is the difference between reflection and refraction?

Reflection: light bounces back from surface following laws of reflection; occurs at surface; angle of incidence = angle of reflection; no change in speed. Refraction: light bends when entering different medium; occurs at interface; bends toward/away from normal depending on density; speed changes. Pencil in water appears bent due to refraction. Reflection in mirrors; Refraction in lenses and transparent materials.

Q4: What is a lens? Explain convex and concave lenses.

Lens: transparent object made of glass/plastic with curved surfaces that refract light. Convex lens: bulges outward; converges parallel rays at focal point (F); real, inverted, magnified image for objects closer than 2F; magnifying glass, camera, projector. Concave lens: curves inward; diverges parallel rays; always produces virtual, erect, diminished image; used in spectacles for myopia (short-sightedness). Focal length (f) = distance from lens to focal point.

Q5: Define angle of incidence and angle of refraction.

Angle of incidence (i): angle between incident ray and normal (perpendicular to surface) at point of incidence. Angle of refraction (r): angle between refracted ray and normal. Angle of reflection (for mirrors): angle between reflected ray and normal = angle of incidence. Normal: imaginary line perpendicular to surface at point of contact. Note: All angles measured from normal, not from surface itself.

Q6: What are the properties of light reflected by a plane mirror?

Properties of image in plane mirror: 1. Virtual: image cannot be caught on screen 2. Erect: image upright, same orientation as object 3. Same size: height of image = height of object 4. Laterally inverted: left and right reversed (write 'PAN' in front of mirror, image appears as backwards 'NAP') 5. Same distance: image distance behind mirror = object distance in front 6. Same light paths: light reflects following laws of reflection

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