Question

Ellen wears eyeglasses with the prescription$-1.0D$.

a. What eye condition does Ellen have?

b. What is her far point without the glasses?

Short answer

a. Ellen has Myopia.

b. The far point without the glasses is$1m$.

Step-by-step solution

Part (a) Step 1: Given Information

we have given that prescription $p=-1.0D$.

We need to find out Ellen's eye condition.

Part (a) Step 2: Simply.

$$\begin{gathered} P=-1D \\ f=\frac{1}{p}=-1m \end{gathered}$$

He is using lens of $f=-ve$diverging lens, so he has myopia.

Part (b) Step 1: Given Information

We need to find out Ellen's far point without the glasses.

Part (b) Step 2: Simplify.

Ellen can see the object at some point $S^{\text{'}}$which is at $\infty$.

$$\begin{gathered} \frac{1}{S}+\frac{1}{S^{\text{'}}}=\frac{1}{f} \\ \frac{1}{S}+\frac{1}{P}=\frac{1}{1m} \\ S=1m\to 100cm \end{gathered}$$