Answer:
length of selfie-stick is 1.62 m
Explanation:
Given data
image size h1 = 5 mm = 5 ×[tex]10^{-3}[/tex] m
focal length = 4 mm = 4 ×[tex]10^{-3}[/tex] m
distance h2 = 2.032 m
to find out
How long of a selfie-stick
solution
here we find first magnification
that is M = h1 /h2
M = 5 ×[tex]10^{-3}[/tex] / 2.032
M = 2.46 ×[tex]10^{-3}[/tex]
and we know M = p/q
so p = Mq = 2.46 ×[tex]10^{-3}[/tex] q
so we apply lens formula
1/f = 1/p - 1/q
1/ 4 ×[tex]10^{-3}[/tex] = 1 / 2.46 ×[tex]10^{-3}[/tex] q - 1/q
q = 1.622 m
so length of selfie-stick is 1.62 m