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 is the algebraic sum of the powers: P = -2 D + (-3 D) = -5 D.
4. A combination of two thin lenses in contact has powers +5 D and -2 D. What is the power of the combination?
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.
5. If two identical lenses, each having power +2 D, are placed in contact, the combined power is:
A.
+1 D
B.
+2 D
C.
+4 D
D.
-4 D
Correct Answer:
+4 D
Explanation:
For identical lenses in contact, their powers add: P = 2 D + 2 D = +4 D.
6. A converging lens of power +6 D and a diverging lens of power -6 D are placed in contact. What is their combined power?
A.
+12 D
B.
-12 D
C.
0 D
D.
+6 D
Correct Answer:
0 D
Explanation:
The powers cancel because P = +6 D + (-6 D) = 0 D.
7. The power of one lens is +3 D and the combined power of two lenses in contact is +8 D. What is the power of the second lens?
A.
+11 D
B.
+5 D
C.
-5 D
D.
+24 D
Correct Answer:
+5 D
Explanation:
Using P = P1 + P2, the second lens power is P2 = 8 D - 3 D = +5 D.
8. Two lenses of powers +1.5 D and +2.5 D are placed in contact. What is their total power?
A.
+1.0 D
B.
+2.0 D
C.
+4.0 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.
9. A lens of power -4 D is combined with a lens of unknown power. If the combination has power +2 D, what is the unknown power?
A.
-6 D
B.
-2 D
C.
+2 D
D.
+6 D
Correct Answer:
+6 D
Explanation:
From P = P1 + P2, the unknown power is P2 = +2 D - (-4 D) = +6 D.
10. When three thin lenses of powers +1 D, +2 D, and -1 D are placed in contact, what is their combined power?
A.
+2 D
B.
+4 D
C.
-2 D
D.
+1 D
Correct Answer:
+2 D
Explanation:
The powers of lenses in contact add algebraically: P = +1 D + 2 D - 1 D = +2 D.
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