Answer:
The lenses with different focal length are four.
Explanation:
Given that,
Radius of curvature R₁= 4
Radius of curvature R₂ = 8
We know ,
Refractive index of glass = 1.6
When, R₁= 4, R₂ = 8
We need to calculate the focal length of the lens
Using formula of focal length

Put the value into the formula



When , R₁= -4, R₂ = 8
Put the value into the formula



When , R₁= 4, R₂ = -8
Put the value into the formula



When , R₁= -4, R₂ = -8
Put the value into the formula



Hence, The lenses with different focal length are four.
The formula that can be used to obtain a convergent series is given by;
a/1 – r.
<h3>What is a series?</h3>
In mathematics, we define a series as sum of numbers which could be convergent or divergent. In a convergent series, the summation of the numbers approaches a given value.
The formula that can be used to obtain a convergent series is given by;
a/1 – r.
Learn more about a convergent series:brainly.com/question/15415793?
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Answer:
B) 0.3Hz
Explanation:
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