Shortcut-Light Chapter (CBSE 10)

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Mirror and lens related formulae:

	Formula	magnification
Mirror	1/f = (1/v) + (1/u)	m=-v/u
Lens	1/f = (1/v) – (1/u)	m=+v/u
Shortcut to remember	Loksabha MP (LMP) (LMP )Lens formula- Minus (LMP )Mirror formula- Plus	MMM- Mirror Magnification formula Minus

 Explanation: 

Mirror Formula 1/f = (1/v) + (1/u)    Lens Formula   1/f = (1/v) – (1/u)

where as f is focal length and image distance is (v) and object distance is (u)

Rule 1: Always write 1/f in LHS.  

Rule2:  In RHS, write 1/v first and 1/u next.

Rule3: In RHS, in between 1/v and 1/u, +ve sign for mirror, -ve sign for lens.

Pneumonics for this:  LMP (Loksabha MP)

(LM)(MP)--> Lens formula - Minus,   Mirror formula - Plus.

Magnification formulae:

Mirror magnification: m =  -v/u ,

Lens Magnification:    m = +v/u, 

 (Note that opposite sign to that of mirror and lens formulae)