ParyavaranHiranyagarbha · Class 11-12
Kaali dhool, pighalti barf: albedo ka khel
Garmi mein kaali t-shirt zyada garam kyun lagti hai — aur iska Himalaya ke glacier se kya lena-dena?
Socho pehle… phir dekho jawab
Kaali satah zyada sunlight sokhti hai, safed zyada wapas bhejti hai. Is 'wapas bhejne' ke hisse ko albedo kehte hain. Taazi barf ka albedo bahut zyada hota hai; par us par kaala carbon (soot) jame, toh woh zyada garmi sokh kar tezi se pighalti hai.
Albedo = reflect hui roshni ÷ aayi hui roshni. Taazi barf bahut zyada reflect karti hai, jabki kaali mitti ya soot bahut kam. Black carbon — adhoora jala hua carbon, jaise lakdi, diesel ya purane bhatthon ka dhuaan — hawa se ud kar barf par baith jaata hai.
Ab feedback loop dekho: barf gandi → kam albedo → zyada garmi sokhi → barf pighli → neeche ki kaali chattaan dikhi → albedo aur kam. Yeh 'positive feedback' hai, jo badlaav ko khud badhata hai. Glacier pighalna nadiyon, pani ki supply aur hydropower sabko chhoota hai.
Trade-off: eenth bhatthe lakhon logon ko rozgaar aur sasti eenthein dete hain. Behtar design (jaise zig-zag kiln, jisme hawa ka flow badal kar jalna zyada poora hota hai) dhuaan kam karta hai, par badlaav ke liye paisa aur training chahiye. Solution mein mazdoor aur maalik dono ko saath lena padta hai.
Ghar pe try karo
Do katori mein ek-ek barf ka tukda rakho. Ek ko kaale kapde se dhako, doosre ko safed se. Dhoop mein rakho aur har 5 minute par dekho kaunsa pehle pighla.
Wow!
Barf ko pighlaane ke liye hamesha garam hawa nahi chahiye — thodi si kaali dhool hi kaafi hai.
3 sawaal
- Albedo kya naapta hai?
Jawab dekho
Satah kitni roshni reflect karti hai. Albedo = reflect hui ÷ aayi hui roshni.
- Black carbon mainly kahan se aata hai?
Jawab dekho
Adhoore dahan (incomplete combustion) se. Soot adhoore jalne ka nateeja hai.
- 'Barf pighli → kaali zameen dikhi → aur pighli' kis tarah ka loop hai?
Jawab dekho
Positive feedback. Badlaav khud ko aur badhata hai, isliye positive feedback.
NCERT se jodo: NCERT Class 11 Geography (Fundamentals of Physical Geography) — solar radiation, heat balance aur temperature