Identify concave and convex mirrors
Scenario
Ek shiny naye chammach (spoon) ko dekho. Uski andar wali side aapko ulta (inverted) dikhati hai, aur bahar wali side seedha (erect).
Same chammach do alag tarah ki images kyun bana raha hai?
Mental model
Cave yani gufa. Andar ki taraf dhasa hua = Concave.
Spherical mirrors ek hollow glass sphere ke kate hue parts hote hain. Agar reflecting surface andar ki taraf mudti hai (gufa/cave jaisi), toh woh concave mirror hai. Agar reflecting surface bahar ki taraf ubhri hui hai, toh woh convex mirror hai.
Explanation
Spherical mirrors do main types ke hote hain: Concave aur Convex. Inhe spherical isliye kehte hain kyunki inka shape ek bade glass ke gole (sphere) ka hissa lagta hai.
Concave mirror ka reflecting surface andar ki taraf curved hota hai, theek ek cave (gufa) ki tarah. Spoon ka andar wala hissa jisme soup bharte hain, concave mirror ki tarah act karta hai. Yeh light rays ko ek point par jama (converge) karta hai, isliye isko converging mirror bhi kehte hain.
Convex mirror ka reflecting surface bahar ki taraf ubhra (bulging out) hota hai. Spoon ka peeche wala hissa convex mirror ka example hai. Yeh light rays ko faila deta hai (diverge), jiske karan isko diverging mirror bola jata hai.
Inke uses inke shape par depend karte hain. Concave mirrors dentist use karte hain daanto ko bada (magnify) dekhne ke liye, aur headlights mein light focus karne ke liye. Convex mirrors gadiyo mein rear-view mirror ke taur par use hote hain kyunki yeh ek choti par seedhi image banate hain jisse wide area dikh jata hai.
Worked example
Problem: A mirror diverges parallel beams of light. What type of mirror is this?
- Jo mirrors light rays ko phaila dete hain (spread out), unhe diverging kehte hain.
Answer: Convex mirror
Problem: A car's headlight uses a mirror to produce a parallel, focused beam of light. Which mirror is used?
- Bulb se aati light ko ek parallel beam banne ke liye hume converging mirror chahiye.
Answer: Concave mirror
Key points
- Concave Mirror: Reflecting surface is curved inwards. Also called a converging mirror.
- Convex Mirror: Reflecting surface is curved outwards. Also called a diverging mirror.
Common mistakes
- Confusing concave and convex: Names ko mix up kar dena aam baat hai. Trick yaad rakho: 'Con-cave' mein 'cave' (gufa) hai, matlab andar ki taraf mudna.
Recall questions
- Which mirror is also known as a diverging mirror?
- The inner curved surface of a shining spoon acts like which mirror?
- Which mirror has its reflecting surface curved inwards?
Questions & answers
Name the type of mirror used in the rear-view mirrors of vehicles.
Convex mirror
Approach: Vehicles need a wider field of view with an erect image, which is provided by a convex mirror.
How can you distinguish between a plane, concave, and convex mirror without touching them?
By looking at your image: plane (same size), concave (magnified when close), convex (diminished).
Approach: Use the characteristics of the virtual images they form.
Continue learning
Next: Define principal focus and focal length