The biconvex lens has both the surfaces

Options

A. convex
B. one plane, one convex
C. one convex, one concave
D. concave

Explanation

**Step-by-Step Solution:**

1. **Understanding the Biconvex Lens:**
- A biconvex lens is a type of lens that is curved outward on both sides. This means that both surfaces of the lens are convex.

2. **Identifying the Options:**
- The options given in the question are:
a) Both surfaces are convex
b) One surface is plane, one surface is convex
c) One surface is convex, one surface is concave
d) Both surfaces are concave

3. **Analyzing Each Option:**
- **Option a:** Both surfaces are convex. This matches the definition of a biconvex lens.
- **Option b:** One surface is plane, one surface is convex. This describes a plano-convex lens, not a biconvex lens.
- **Option c:** One surface is convex, one surface is concave. This describes a convex-concave lens, not a biconvex lens.
- **Option d:** Both surfaces are concave. This describes a biconcave lens, which is also not a biconvex lens.

4. **Conclusion:**
- The only correct option that accurately describes the surfaces of a biconvex lens is that both surfaces are convex.

5. **Final Answer:**
- The correct answer is: **Both surfaces are convex.**

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