A short linear object of length b lies along the axis of a concave mirror or focal length f at a distance u from the pole of the mirror. The size of t

Correct Answer - B (b) we have, `1/f=(1.5-1)(1/10+1/10)` `therefore` Focal length, f= 10 cm Radius of curvaature, R=2f=20 cm

Correct Answer - A (a) We have, `1/v-1/u=1/f` `rArr1/v-1/20=1/(-15)` v=-60 m Image speed=`(v^(2)/u^(2))` (object speed) `=(60/20)^(2)(5)`=45 m/s

Correct Answer - A We know that, linear magnification, `m=(f)/(f-u)` Given object displaced, u=-20cm m=-3 (`therefore "all images aer inverted"`) `So, -3=(f)/(f-(-20))` `-3=(f)/(f+20) Rightarrow -3f-60=f` `4f=-60 Rightarrow f=-(60)/(4)=-15cm` Since, mirror is...

Correct Answer - A Given `f=-f Rightarrow v=(1)/(3)u` According to the lens formula, `(1)/(f)=(1)/(v)-(1)/(u)-(1)/(f)=(1)/((-1//2)u)+(1)/(u)-(1)/(f)` `(-3+1)/(u)-(1)/(f)=-(2)/(u) Rightarrow u=2f`

Correct Answer - C Focal length of a mirror does not depend on the medium in which mirror is held. It depend on the radius of the sphere from which it...

Correct Answer - B Image formation by concave mirror when object is real & placed at focus f. forms image at infinity but not in other cases.

Correct Answer - (A)-q (B)-p (C)-s (D)-r m= `(f)/(f-u)` (A) Convex mirror u=-ve ,f=+ve `m = (f)/(f-(f)) = (1)/(2)` (B) Concave `rarr m = (-f)/(-f-(-f))= oo` (C) Concave mirror u= -...

Correct answer is (d) Zero At c, object produces same sized image. ∵ f = 15 cm, ∴ R = 30 cm object and image both are at c. therefore, distance between them is zero.

Correct Answer - D `(1)/(f)=(1)/(f_(1))+(1)/(f_(2))-(d)/(f_(1)f_(2))=0` `= (1)/(25)+(1)/(-20)-(d)/(-500)=0=(20-25)/(500)=-(d)/(500)` `d=5 cm`

Correct Answer - A For `m=2` `m=(v)/(u)=2` `V=-2u` ………………..`(i)` `(1)/(f)=(1)/(v)+(1)/(u) rArr (1)/(f)=(1)/(-2u)+(1)/(u)` `rArr (1)/(f)=(1)/(2u) rArr u=(f)/(2)` `& v=-f` Distance between object `&` image `=f+f//2=3f//2` For `m=-2` `m=-(v)/(u)=-2` `v=2u` `rArr (1)/(f)=(1)/(2u)+(1)/(u) rArr...