Question

question 5 plz solve it fast

Answer 1

focal length is 4.5 and the mirror is concave
magnification=h(image)/h(object)=-v/u
so h(image)=1(assume) than h(object)=1/5
so-v/u=hi/ho(u=18)(given)
by putting all values we get v =-18/5
than applying the formula 1/v+1/u=1/f(keep sign convention in mind u=-ve,v=-ve)
now putting the value of u=-18 and v=-18/5
we get value of f is -18/4 so the focal length being -ve due to which mirror is concave(you should know)