Question

an object of 5cm length is placed at a distance of 30cm in front of concave mirror of focal lenght 20cm find psition and size of image

Answer 1

let length or height of object H=5cm , then mirror is concave so (u=-30)cm And focal length =-20cm,now we hawh,ve to find v and h, using mirror formulae 1/v +1/u=1/f .1/v-1/30 = -1/20 . 1/v= -1/20+1/30 =-3+2/60=-1/60. so v =-60. magnificication h/H=-(v/u),h/5=-(-60/-30),= h/5=-2, h=-10cm.