Solar Energy Questions and Answers – Solar Day Length

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This set of Solar Energy Multiple Choice Questions & Answers (MCQs) focuses on “Solar Day Length”.

1. What is solar noon?
a) Time of the day at which sun’s rays are perpendicular to a given line of longitude
b) Time of the day at which sun’s rays are parallel to a given line of longitude
c) Time of the day at which sun’s rays are perpendicular earth’s surface
d) Time of the day at which sun’s rays are parallel to earth’s surface
View Answer

Answer: a
Explanation: Solar noon is defined as the time of the day at which sun’s rays are perpendicular to a given line of longitude. It is important to note that solar noon does not occur simultaneously at every location on earth. Hence the phrase, “give line of longitude”.
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2. How does the solar noon vary with every 15 degrees of longitude east of a given longitude?
a) Solar noon occurs one hour late with every 15 degrees of longitude east of a given longitude
b) Solar noon occurs one hour earlier with every 15 degrees of longitude east of a given longitude
c) Solar noon occurs does not vary with longitude
d) Solar noon occurs half hour late with every 15 degrees of longitude east of a given longitude
View Answer

Answer: b
Explanation: Solar noon varies with longitude but it is important to mention the reference longitude for correct calculation. It occurs one hour late with every 15 degrees of longitude east of a given longitude. This can be used to estimate the time of different regions.

2. How does the solar noon vary with every 15 degrees of longitude west of a given longitude?
a) Solar noon occurs one hour later with every 15 degrees of longitude west of a given longitude
b) Solar noon occurs one hour earlier with every 15 degrees of longitude east of a given longitude
c) Solar noon occurs one hour later with every 15 degrees of longitude west of a given longitude
d) Solar noon occurs half hour later with every 15 degrees of longitude west of a given longitude
View Answer

Answer: c
Explanation: To calculate solar noon, it is important to mention the reference longitude. Once the reference is known, solar noon occurs one hour later with every 15 degrees of longitude west of a given longitude.
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4. What is a solar day?
a) One complete revolution of sun around moon
b) One complete revolution of earth around sun
c) One complete revolution of moon around earth
d) One complete revolution of sun around earth
View Answer

Answer: d
Explanation: Though the earth revolves around the sun and rotates about its own axis, a solar day is measured with respect to an observer on earth. Hence, a solar day is defined as one complete revolution of sun around earth.

5. What is a sidereal day?
a) Time taken by earth to rotate about its axis for distant stars to appear fixed
b) Time taken by earth to rotate about its axis for sun to appear fixed
c) Time taken by earth to rotate about its axis for distant stars to be moved by 1 degree
d) Time taken by earth to rotate about its axis for distant stars to be moved by 0.5 degrees
View Answer

Answer: a
Explanation: Sidereal day is the time taken by earth to rotate about its axis for distant stars to appear fixed. Time taken by earth to rotate about its axis for sun to appear fixed is solar day.
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6. Solar day is ______ sidereal day.
a) 4 min shorter than
b) 4 min longer than
c) 10 min shorter than
d) 10 min longer than
View Answer

Answer: b
Explanation: Solar day is 4 min longer than sidereal day. This calculation is based on the time taken by earth to complete one rotation about its axis and one revolution about sun.

7. One sidereal day is ______ solar hours and ______ solar minutes long.
a) 26, 57
b) 24, 59
c) 23, 56
d) 24, 60
View Answer

Answer: c
Explanation: One solar day is 24 hours long and one sidereal day is 24 hours long. However, one sidereal day is 24 solar hours and 60 solar minutes long. Thus, there is a difference of 4 minutes between the two.
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8. Which of the following solar time duration is not constant throughout the year?
a) Mean solar day
b) Sidereal day
c) Local true solar time
d) Apparent solar day
View Answer

Answer: d
Explanation: Apparent solar day is not constant throughout the year. It can be 20 seconds shorter or 30 seconds longer than a mean solar day. Sidereal day is not a solar time.

9. What is local true solar time?
a) Equivalent of earth’s solar time on other planets
b) Solar time on every location of earth
c) Solar time on the Greenwich meridian
d) Solar time on the equator
View Answer

Answer: a
Explanation: Local true solar time (LTST) is the equivalent of earth’s solar time on other planets. On earth, solar time was used to be measured by sundials.
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10. The length of mean solar day is slowly increasing.
a) True
b) False
View Answer

Answer: a
Explanation: The length of a mean solar day is slowly increasing. This is because of the tidal acceleration of the moon by earth and the corresponding slowing of earth’s rotation by moon.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter