Earth, Moon, and the Sun Part 3: MCQs (Q51–Q75)
Part 3 — Moon: Phases, Phases Cycle & Relative Motions (Questions 51–75)
51. The Moon completes one revolution around the Earth roughly in:
A. 24 hours
B. 27.3 days (sidereal month) ✅ Correct answer: B
C. 365 days
D. 7 days
Explanations:
A) That’s Earth’s rotation period — incorrect.
B) Correct — sidereal month (relative to stars) ~27.3 days; synodic month (~29.5 days) measures phases.
C/D) Incorrect.
52. The phase cycle of the Moon (new moon → new moon) takes about:
A. 24 hours
B. 29.5 days (synodic month) ✅ Correct answer: B
C. 365 days
D. 7 days
Explanations:
A/C/D) Incorrect.
B) Correct — time between identical lunar phases ≈ 29.5 days.
53. A New Moon occurs when:
A. Earth is between Sun and Moon
B. Moon is between Sun and Earth (Moon’s illuminated side faces away from us) ✅ Correct answer: B
C. Half of Moon is lit and visible
D. Moon is full and bright
Explanations:
A) That configuration gives lunar eclipse/full moon — incorrect.
B) Correct — new moon near conjunction; dark side faces Earth.
C/D) Incorrect.
54. A Full Moon occurs when:
A. Moon between Sun and Earth
B. Earth between Sun and Moon (Moon fully illuminated as seen from Earth) ✅ Correct answer: B
C. Moon is invisible
D. Sun and Moon on same side of Earth
Explanations:
A) New moon, not full — incorrect.
B) Correct — full moon at opposition.
C/D) Incorrect.
55. Crescent moon means:
A. Moon fully lit.
B. Only a thin sliver (less than half) of Moon’s visible face is illuminated. ✅ Correct answer: B
C. Always half-lit.
D. Moon missing permanently.
Explanations:
A/C/D) Incorrect.
B) Correct — crescent phases before/after new moon.
56. The main cause of the phases of the Moon is:
A. Earth’s shadow falling on Moon always
B. Changing relative positions of Sun, Moon and Earth causing different illuminated portions to be visible ✅ Correct answer: B
C. Moon’s own light varying intensity
D. Clouds only
Explanations:
A) Earth’s shadow causes lunar eclipses only sometimes — incorrect.
B) Correct — lit portion visible changes as Moon orbits Earth.
C/D) Incorrect.
57. When the Moon is at first quarter, the portion of the Moon visible from Earth is:
A. Fully dark
B. Half illuminated (right half in Northern Hemisphere) ✅ Correct answer: B
C. Fully lit (full moon)
D. New (invisible)
Explanations:
A/C/D) Incorrect.
B) Correct — first quarter shows half moon.
58. The Moon rotates on its axis in the same time it revolves around Earth, which causes:
A. Moon’s far side always visible
B. Same face of Moon always faces Earth (synchronous rotation) ✅ Correct answer: B
C. Moons of Jupiter to vanish
D. Earth to stop rotating
Explanations:
A) Far side is never seen from Earth — incorrect phrasing.
B) Correct — synchronous rotation (tidal locking).
C/D) Irrelevant.
59. Which feature explains why we always see nearly the same face of Moon?
A. Moon’s axis tilted by 90°
B. Moon is tidally locked with Earth (rotational period = orbital period). ✅ Correct answer: B
C. Earth’s moon doesn’t rotate at all
D. Sun’s gravity keeps one face bright always
Explanations:
A/C/D) Incorrect.
B) Correct.
60. A waxing Moon is:
A. Getting smaller in illuminated portion each night.
B. Getting larger in illuminated portion each night (from new → full). ✅ Correct answer: B
C. The same every night.
D. Invisible always.
Explanations:
A) That’s waning — incorrect.
B) Correct — waxing from new to full.
C/D) Incorrect.
61. A waning Moon means:
A. Illuminated area is decreasing after full moon. Correct answer: A ✅
B. Illuminated area increasing every night.
C. Moon is invisible permanently.
D. Moon is moving away extremely fast.
Explanations:
A) Correct — waning from full back toward new.
B/C/D) Incorrect.
62. Why does the Moon not produce its own light?
A. It is too small.
B. It reflects sunlight — it is not a luminous body. ✅ Correct answer: B
C. It is cold and cannot emit light.
D. It’s made of dark matter.
Explanations:
A/C/D) Irrelevant or wrong.
B) Correct — Moon’s brightness is reflected sunlight.
63. Which phase of Moon is necessary for a solar eclipse to occur?
A. Full Moon
B. New Moon ✅ Correct answer: B
C. First quarter
D. Last quarter
Explanations:
A) Lunar eclipse needs full moon — incorrect.
B) Correct — solar eclipse occurs when Moon between Sun and Earth (new moon).
C/D) Incorrect.
64. Which phase is necessary for a lunar eclipse to occur?
A. New Moon
B. Full Moon ✅ Correct answer: B
C. Crescent
D. First quarter
Explanations:
A/C/D) Incorrect.
B) Correct — lunar eclipse occurs when Earth between Sun and Moon.
65. The “Man on the Moon” image is visible because:
A. Moon emits light in shapes.
B. Dark and light regions on Moon (maria and highlands) reflect different amounts of sunlight forming patterns visible from Earth. ✅ Correct answer: B
C. Clouds on Earth project patterns.
D. Moon is transparent.
Explanations:
A/C/D) Incorrect.
B) Correct — surface features produce recognizable patterns.
66. Which statement about lunar phases and time is TRUE?
A. Phases change every hour.
B. It takes about 29.5 days for the same phase to reoccur (synodic month). ✅ Correct answer: B
C. Phases are due to Earth’s shadow every night.
D. Phases remain constant at high latitudes only.
Explanations:
A/C/D) Incorrect.
B) Correct.
67. The change from full moon to new moon is called:
A. Waxing
B. Waning ✅ Correct answer: B
C. Eclipse
D. Revolution only
Explanations:
A) Waxing is new → full — incorrect.
B) Correct — waning is full → new.
C/D) Not the correct term.
68. Which lunar phase is visible approximately one week after a new moon?
A. Full Moon
B. First quarter (half moon) ✅ Correct answer: B
C. New Moon again
D. Waning crescent
Explanations:
A) Full moon ~2 weeks after new — incorrect.
B) Correct — about 7–8 days after new, first quarter appears.
C/D) Incorrect timing.
69. If the Moon is directly between the Sun and Earth and not perfectly aligned, what type of solar eclipse occurs?
A. Total lunar eclipse
B. Partial solar eclipse ✅ Correct answer: B
C. Annular eclipse only
D. No eclipse ever occurs
Explanations:
A) Lunar eclipse occurs when Earth between Sun and Moon — incorrect.
B) Correct — imperfect alignment causes part of Sun blocked → partial.
C) Annular occurs when Moon too far to fully cover Sun; could be also if alignment central but apparent sizes differ — but partial is general case — B best.
D) Incorrect.
70. The side of the Moon that faces away from Earth is called:
A. Near side
B. Dark side (misleading)
C. Far side ✅ Correct answer: C
D. Invisible side permanently (wrong phrasing)
Explanations:
A/B/D) Misleading or incorrect.
C) Correct — “far side” faces away; all parts get sunlight sometime, so “dark side” is misleading.
71. Which phenomenon proves that Moon revolves around Earth?
A. Daily sunrise/sunset only
B. Change of lunar phases and monthly motion among stars ✅ Correct answer: B
C. Explosion of Moon occasionally
D. Tides vanish at full moon
Explanations:
A/C/D) Incorrect.
B) Correct — phases and shifting position against background stars show orbit.
72. Which statement is CORRECT about synodic and sidereal months?
A. They are identical in length.
B. Synodic month (~29.5 d) is time between similar phases; sidereal month (~27.3 d) is orbital period relative to stars. ✅ Correct answer: B
C. Sidereal month is 365 days.
D. Synodic month is one day only.
Explanations:
A/C/D) Incorrect.
B) Correct.
73. Tidal bulges on Earth’s oceans are mainly caused by:
A. Wind only
B. Gravitational pull of Moon (and Sun) on Earth ✅ Correct answer: B
C. Shape of clouds only
D. Earth’s magnetic field only
Explanations:
A/C/D) Not main causes.
B) Correct — lunar gravity causes tides; Sun also contributes.
74. A lunar eclipse can be seen by:
A. Only people in the shadow of Moon on Earth
B. Anyone on the night side of Earth when the eclipse occurs ✅ Correct answer: B
C. Only people at noon
D. Nobody — they are invisible
Explanations:
A) Lunar eclipse is Earth’s shadow on Moon; observers on night side can see it — B is correct.
C/D) Incorrect.
75. The reason we do not have solar eclipses every new moon is:
A. New moons are rare.
B. Moon’s orbit is inclined about 5° to Earth’s orbital plane so alignment is not always exact. ✅ Correct answer: B
C. Sun blocks eclipses much of year.
D. Earth’s rotation prevents eclipse observation.
Explanations:
A/C/D) Incorrect.
B) Correct — orbital inclination prevents monthly alignments.