When a photograph is taken, the exposure time, t is directly proportional to the square of the size, f , of the opening in the camera lens. t = 0.02 when f = 8. It can be shown that t = 1/3200 f squared. Calculate the value of f when t = 0.0098

Respuesta :

Answer:

f = 5.6

Step-by-step explanation:

given the quantities are proportional then the equation relating them is

t = kf² ← k is the constant of proportionality

To find k use the condition t = 0.02 when f = 8

k = [tex]\frac{t}{f^{2} }[/tex] = [tex]\frac{0.02}{64}[/tex] = [tex]\frac{1}{3200}[/tex]

t = [tex]\frac{f^{2} }{3200}[/tex] ← equation of proportionality

when t = 0.0098, then

0.0098 = [tex]\frac{f^{2} }{3200}[/tex] ( multiply both sides by 3200 )

f² = 0.0098 × 3200 ( take the square root of both sides )

f = [tex]\sqrt{0.0098(3200)}[/tex] = 5.6