1. Two thin lenses of powers +2 D and +3 D are placed in contact. What is their combined power?
A.
+1 D
B.
+5 D
C.
-1 D
D.
+6 D
Correct Answer:
+5 D
Explanation:
For thin lenses in contact, the combined power is the sum of their individual powers: P = P1 + P2 = 2 D + 3 D = +5 D.
2. A lens of power +4 D is placed in contact with a lens of power -1 D. What is the combined power?
A.
+5 D
B.
-5 D
C.
+3 D
D.
-3 D
Correct Answer:
+3 D
Explanation:
Using the power addition rule, P = P1 + P2 = +4 D + (-1 D) = +3 D.
3. Two lenses in contact have powers -2 D and -3 D. Their combined power is:
A.
-5 D
B.
+5 D
C.
-1 D
D.
+1 D
Correct Answer:
-5 D
Explanation:
The combined power equals the algebraic sum of the powers: P = -2 D + (-3 D) = -5 D.
4. A combination of two lenses in contact has powers +6 D and -6 D. What is its total power?
A.
+12 D
B.
-12 D
C.
0 D
D.
+6 D
Correct Answer:
0 D
Explanation:
The powers cancel each other because P = +6 D + (-6 D) = 0 D.
5. If two identical lenses, each having power +2 D, are placed in contact, their combined power is:
A.
+2 D
B.
+4 D
C.
-4 D
D.
0 D
Correct Answer:
+4 D
Explanation:
For identical lenses in contact, the powers add: P = +2 D + +2 D = +4 D.
6. A converging lens has power +5 D and a diverging lens has power -2 D. What is the power of the combination when they are in contact?
A.
+7 D
B.
-7 D
C.
+3 D
D.
-3 D
Correct Answer:
+3 D
Explanation:
Applying the power addition rule gives P = +5 D + (-2 D) = +3 D.
7. Two thin lenses in contact have a combined power of +8 D. If one lens has power +3 D, what is the power of the other lens?
A.
+11 D
B.
+5 D
C.
-5 D
D.
-11 D
Correct Answer:
+5 D
Explanation:
Since P = P1 + P2, the unknown power is P2 = 8 D - 3 D = +5 D.
8. The combined power of two lenses in contact is -4 D. If one lens has power +2 D, what is the power of the other lens?
A.
-6 D
B.
-2 D
C.
+6 D
D.
+2 D
Correct Answer:
-6 D
Explanation:
Using P2 = P - P1, the second lens has power -4 D - (+2 D) = -6 D.
9. What is the combined power of lenses with powers +1.5 D and +2.5 D placed in contact?
A.
+1.0 D
B.
+4.0 D
C.
-1.0 D
D.
-4.0 D
Correct Answer:
+4.0 D
Explanation:
The total power is the sum of the individual powers: P = +1.5 D + +2.5 D = +4.0 D.
10. A lens combination in contact contains lenses of powers -1.5 D and +4.5 D. What is the power of the combination?
A.
-6.0 D
B.
+6.0 D
C.
+3.0 D
D.
-3.0 D
Correct Answer:
+3.0 D
Explanation:
By the power addition rule, P = -1.5 D + 4.5 D = +3.0 D.
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