NCERT Solutions Class 8 Science Chapter 10: Light: Mirrors and Lenses (Hinglish)

Curiosity, Class 8 Science textbook (Reprint 2026-27), ke Chapter 10, Light: Mirrors and Lenses, ke har sawaal ke jawaab: Probe and ponder, Activities 10.1 se 10.11 aur text ke sawaal, Keep the curiosity alive ke saare baarah sawaal, aur Discover, design, and debate. Page numbers book ke hisaab se hain (pages 152–169). Chhote notes: Chapter 10 ke notes.

Probe and ponder (page 152)

Kya darpan bade ya chhote pratibimb de sakte hain? Haan. Avtal darpan paas rakhi vastu ka bada pratibimb deta hai, aur uttal darpan hamesha chhota pratibimb deta hai.

Side-view mirror par cheezon ke zyada paas hone ki chetaavni kyon? Ye darpan uttal hote hain. Peechhe ki sadak ka chauda drishya dikhaate hain, par har gaadi asal se chhoti dikhti hai aur isliye door lagti hai. Chetaavni driver ko doori ka galat andaaza lagaane se rokti hai.

Kuch padhne ke chashmon par mudi rekha. Aise chashmon (bifocals) mein do alag lens wale hisse hote hain: upar wala door dekhne mein aur neeche wala paas padhne mein madad karta hai. Rekha wo jagah hai jahan dono lens milte hain.

Golaakaar darpan aur unke pratibimb (pages 153–157)

Activity 10.1. Haan, chammach darpan ki tarah kaam karta hai. Andar mude hisse mein chehre ka pratibimb ulta hota hai; baahar ubhre hisse par seedha par chhota. Chammach door karne par pratibimb ka size badalta hai. Chammach ke do hisse avtal aur uttal darpan ki tarah vyavhaar karte hain.

Activity 10.2. Aankh ke star par bagal se dekhne par avtal darpan ki sateh andar dhansti aur uttal ki baahar uthti dikhti hai.

Activity 10.3. Khilauna 3–4 cm door ho to avtal darpan seedha, bada pratibimb aur uttal darpan seedha, chhota pratibimb dikhaata hai; dono mein paarshv parivartan hai. Khilauna door jaane par avtal darpan ka pratibimb ulta ho jaata hai, pehle bada phir chhota, jabki uttal darpan ka pratibimb seedha rehta aur thoda chhota hota hai. Nishkarsh: samtal darpan ke ulat, golaakaar darpan ka pratibimb doori ke saath badalta hai, aur sirf avtal darpan use ulta kar sakta hai.

Ye kahan istemaal hote hain? Avtal: torch aur headlight ke reflector, dentist ke darpan, doorbeen. Uttal: side-view mirror, modon aur chauraahon par sadak suraksha darpan, aur dukaanon ke nigraani darpan.

Paraavartan ke niyam (pages 157–160)

Activity 10.4. Haan, aapatit kirnpunj khisakne par paraavartit kirnpunj bhi khisakti hai. Table 10.1 ke namoona maan: i = 20°, r = 20°; i = 35°, r = 35°; i = 50°, r = 50° (chhote antar kheenchne aur naapne se aate hain). Abhilamb ke saath padi kirnpunj ke liye dono kon 0° hain.

Activity 10.5. Nahi: kaagaz ka baahar nikla hissa modne par paraavartit kirnpunj us par nahi dikhti; seedha karne par laut aati hai. Aapatit kiran, abhilamb aur paraavartit kiran ek hi tal mein hain.

Activity 10.6. Haan, Fig. 10.11 jaisa hi dikhta hai: samtal darpan se lauti kirnein samaanaantar rehti hain, avtal se milti hain aur uttal se failti hain.

Activity 10.7. Haan. Kuch minute mein chamakta bindu kaagaz se dhuaan nikaalta hai aur wo jal bhi sakta hai, kyunki avtal darpan dhoop ko us chhote bindu par ikattha karta hai.

Lens (pages 161–165)

Activity 10.8. Paani ki boond ki sateh baahar mudi hai. Uske theek neeche ke akshar bagal ke aksharon se bade dikhte hain: boond saade uttal lens ka kaam karti hai.

Activity 10.9. Uttal lens se paas ki vastu seedhi aur badi dikhti hai; door jaane par ulti, pehle badi phir chhoti. Avtal lens se hamesha seedhi aur chhoti. Nishkarsh: uttal lens doori ke hisaab se bada aur ulta kar sakta hai, jabki avtal lens cheezon ko hamesha chhota aur seedha dikhaata hai.

Activity 10.10. Nahi, sirf patli kaanch ki plate se kirnpunj bina badle guzarti hai. Uttal lens kirnon ko milaata hai aur avtal lens failaata hai.

Activity 10.11. Haan, dhoop mein pakda uttal lens use chamakte bindu par ikattha karke kaagaz jala sakta hai, avtal darpan ki tarah. Lens se Suraj ko kabhi mat dekho.

Keep the curiosity alive (pages 166–169)

1. (ii) 50°. Paraavartit kiran abhilamb se 40° banaati hai, isliye darpan se 90° − 40° = 50°.

2. (a) Paraavartit kiran abhilamb ke saath seedhi waapas jaati hai: paraavartan kon 0°. (b) Ye bhi apne hi raaste lautti hai, kyunki jhuke darpan ke abhilamb ke saath padti hai: 0°. (c) Ye abhilamb se 20° par, doosri taraf nikalti hai: 20°.

3. (i) Dhakkan chhota aur seedha: uttal darpan. (ii) Bada aur seedha: avtal darpan. (iii) Barabar size: samtal darpan.

4. (i) Bada: uttal lens. (ii) Chhota: avtal lens. (iii) Barabar: samtal paardarshi kaanch.

5. (ii) Aapatan kon 0° hai (paraavartan kon bhi; prakaash seedha laut jaata hai).

6. Baayaan darpan: graph ke khaane chhote dikhte hain, isliye uttal darpan. Beech wala: khaane sheet jaise hi, isliye samtal darpan. Daayaan: khaane bade, isliye avtal darpan.

7. (iii). Door se use ulta pratibimb dikhta hai jo paas aane par badhta jaata hai; darpan ke bahut paas ye seedha aur bada ho jaata hai.

8. Akshar se kuch centimetre upar pakadne par magnifying glass akshar seedhe aur bade dikhaata hai. Door karne par akshar badhte hain, phir dhundhle hote hain, aur usse aage ulte aur chhote dikhte hain. Magnifying glass ek uttal lens hai.

9. (i)–(a), (ii)–(b), (iii)–(c), (iv)–(d).

10. (i). Dono sahi hain aur Reason, Assertion ko samjhaata hai: uttal darpan peechhe ke kahin bade kshetra ka seedha pratibimb deta hai.

11. (ii). Fig. 10.27(a) mein pratibimb seedha par vastu se chhota hai, jaisa uttal darpan mein; (b) mein seedha aur bada, jaisa paas rakhi vastu ke saath avtal darpan mein.

12. Paani se dikhne wala pencil ka hissa mota dikhta hai, aur paani ki sateh par khiska hua lag sakta hai, jabki upar ka hissa saamaanya dikhta hai. Paani bhara gol gilaas uttal lens ki tarah kaam karta hai: pencil se aata prakaash isse guzarte hue mudta hai, isliye pencil bagal mein badi dikhti hai.

Discover, design, and debate (page 169)

Doctor ke darpan: dentist daanton ka bada drishya dekhne ke liye handle wala chhota avtal darpan lete hain; ENT doctor paaramparik roop se maathe par avtal darpan pehante hain jo kaan, naak ya gale mein roshni ikattha karta hai. Solar cooker ka prastaav: jaise lakdi ya gatte ka box cooker, andar kaala bartan, kaanch ka dhakkan aur chamakti panni lagi dhakkan-patti jo dhoop andar bheje, ya mude darpanon ki thaali jo dhoop ko bartan par ikattha kare; prastaav mein saamaan, size, rakhne ki jagah, kitne logon ke liye, aur har cheez ki keemat likho. Virtual prayog: kisi ray-optics simulation mein vastu ko avtal darpan ya uttal lens ke paas laane par pratibimb ulte se seedha aur bada hota dikhta hai.

Hamari vaigyanik virasat. Bhaskara II ke samay ke khagolvid uthle katoron ke paani mein taaron aur grahon ke pratibimb sahi kon par lagi naliyon se dekhkar unki sthiti naapte the; unke tareeke dikhaate hain ki ve paraavartan ka niyam vyavhaar mein istemaal karte the.