Keeping in mind the difficulty of the subject we have summarized the most important questions of physics which can be asked to be answered in exams.
These questions of physics fall in the category of most important.
- Assuming that the atmosphere is free from heavy clouds, how is it that the stars can not be seen during day time, while, they can be seen under similar conditions from the bottom of fairly deep vertical shaft of a coal-mine?
The light of the stars is too feeble to be seen in the face of too bright diffused light of the sun pervading the atmosphere during day time. Therefore, we can not see stars during day light. Stars can be seen only when the light of the sun vanishes and the light of the stars can reach us.
While looking at the sky from the bottom of a deep vertical shaft of a coal mine, similar conditions are brought about. As blackness absorbs all the light falling on it and does not reflect any portion of it back, the diffused light of the sun get absorbed by the black walls of the shaft and none of it reaches the observer at the bottom.
On the other hand the light of the stars vertically above the shaft goes directly down the sun through the air without anywhere touching the walls. Thus the stars become visible from the bottom of a shaft.
- Give a list of various calendars which have been in use?
Calendar is the mood of adjusting the natural divisions of time with respect to each other for the purpose of civil life. An almanac is table of months, days and seasons, or of special facts etc.
Counting of months, days and seasons began very early in man’s history.
- How fast does the earth rotate?
- The earth does not rotate at the poles. At the equator it rotates with a speed of about one thousand and thirty miles per hour. At other places the speed varies uniformly between the above limits.
- How hot is the sun?
It is said that the surface temperature of the sun is some eleven thousand degrees Fahrenheit. No substance can exist in the form of solid or in liquid state within one lacks miles of it. The inside of the sun is said to be still hotter, even up to eighty million degrees Fahrenheit. It is held that the heat can burn our earth to smoke and ash instantaneously.
These are the important questions of physics which could be asked in exams.
- If an enormous explosion takes place on the moon about how long will it take to be heard on the earth?
It will never be heard on the earth. Sound does not travel through empty space. As such it can not reach the atmosphere surrounding the earth.
- If the sun suddenly ceases to send out light to the earth, how long will it take for the change to be noticed on the earth?
It will take 8 ½ minutes to be noticed on the earth.
Types of constellations is one of the frequently asked questions in physics competitive exams so it is significantly important.
- What are constellations? And what are the names of some important constellations?
Group of stars which are concentrated here and there in space forming some imaginary figures are termed as constellations. In the north there is a group of seven stars popularly recognized by most of the people.
The list of some important constellations is given below:-
Great Bear, Plough or Urea Major
Cassiopeia (broken W-shaped)
Ciphers (inverted temple-shaped)
Orion (man with gun-shaped)
- What are the kinds of year?
The year is of three kinds.
It is the period of sun’s revolution in the elliptic from vernal equinox to vernal equinox back.
It is the period of complete revolution of the sun in the ecliptic relative to any fixed star free from proper motion.
It is the period of suns complete revolution in its ecliptic orbit around the earth (apparently) form perigee t perigee back or from apogee to apogee back.
- What is Aurora?
Aurora is a luminous meteoric phenomenon of electrical character seen in and towards the Polar Regions, with tremendous motion and giving forth streams of light.
Aurora Borealis or Septentrionalis are the northern aurora or northern lights and Aurora Australis are the southern lights.
- What is meant by space research?
By space research we means scientific research work which can only be carried out by means of equipments carried to otherwise inaccessible observing locations by rocket propulsion. Such propulsion does not place reliance on the presence of an atmosphere to provide oxygen so that it is capable in principle of conveying objects to unlimited distances.
Thus the subject of space research is concerned with scientific applications in various fields of a single highly specialized and powerful technique. It can provide data of great importance such as the physics of the earth, the sun, moon and other bodies of the solar system, astronomy, geodesy, and the study of gravitation.
The prospect of investigating the biological conditions on different planets such as Mars and Venus is also opened, as well as that of experimental biological studies under conditions of zero gravity. Although the results of many aspects of the space research are vital for those concerned with the practical realization of manned travel in space, space research is largely a branch of pure science independent of any applications which may stem from it.
- What is meant by the following terms?
Solar day, sidereal time, sidereal day
The interval between two successive transits of the centre of the sun over the meridian of an observer or an observatory is called an apparent solar day.
The hour angle of the true vernal equinox at any instant at any place is called an apparent (true) sidereal time at that place. The hour angle of the mean vernal equinox at any instant is called the mean sidereal at that instant.
An apparent sidereal day is the interval between two consecutive transits of a star over the meridian of an observer or of an observatory.
- What is Stratosphere and Bathysphere?
The Stratosphere is the upper portion of the atmosphere about a height of some seven miles. There the temperature changes but little with altitude.
The Bathysphere is a hollow steel driving sphere with glass windows used by William Beebe for observing marine life under natural conditions.
- What is the data that space research has furnished in respect of the earth’s upper atmosphere?
Before the introduction of space rockets the greatest altitudes attainable by balloons was about 20 miles. Much of great scientific interest remained to be investigated at greater altitudes.
It has been discovered that near the 60 mile level a number of atmospheric phenomenon occur. Above this level the oxygen becomes predominantly monatomic in contrast to the normal diatomic form at lower altitudes. The ionosphere, a region in which concentration of free electrically charged particles, electrons and positive ions occur in sufficient concentration to affect substantially the propagation of radio waves through the region, extends upwards from a height of 60 miles to several hundred miles. It is most concentrated at an altitude over 200 hundred miles. Meteors are mainly burnt up near the 60 mile level though very small micrometeorites, fine dust less than 10-3mm. Diameter do not heat up sufficiently through atmospheric friction to evaporate and gradually settle on the surface.
To bright atmospheric glows which are observed in the sky near polar latitudes, the northern aurora borealis and the southern aurora australis are most frequently observed at altitudes near 60 miles but do not extend at times to such higher altitudes. There exists also a much weaker glow, the night air glow, which does not depend strongly on geographical location.
The behavior of the upper atmosphere is strongly influenced by the sun. The electromagnetic radiation emitted continually by the sun is responsible, through its effect on atmospheric atoms and molecules, for the production of the ozone layer, the dislocation of diatomic to produce monatomic oxygen, the ionosphere, and the air glow.
When in a disturbed state the sun emits streams of electrically charged particles which produce the aurora displays and a number of associated effects, which includes disturbances of the compass needle which when great enough are known as magnetic storms, and disturbances of the ionosphere, particularly in polar latitudes. The marked concentration of the effect near polar latitude is due to the influence of the earth’s magnetic field on the streams of charged particles which produce the phenomenon.
- What is the difference between a planet and a star? (a simple but one of the common important questions asked from intermediate physics students)
A planet is a cold body, and gives only reflected light received from the sun. The planets are the members of the solar system. Their motions are mainly governed by the attraction of the sun. If you look through a telescope their surfaces appear as discs.
A star on the other hand shines or gives out light because it is white hot. They are outside the solar system. The nearest star is farther away than the farthest planet. Owing to their being far away, all the stars, even to the most powerful telescope, appear nothing but points of light.
The sun is a star quite a small one, and must be excluded from these statements.
- What is zodiac?
Zodiac is the belt of firmament enclosing the circuit over which the principle planets travel. It is divided into twelve equal spaces of thirty degrees each, comprising respectively the twelve signs of the zodiac i.e. Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorns, Aquarius and Pisces.
- Who was the first man to measure the circumference of the earth accurately?
Eratosthenes, in the third century B.C., came with about 200 miles of the measurement now accepted.
- Why do leap years have 336 days? (this type of questions are important because these are asked in the physics portion of recruitment exams)
The earth journeys around the sun takes about 365 ¼ days. Every fourth year one day more is added to February. This, approximately balances matters, although not quit exactly.
- Why does the moon give light at night? Is the moon bigger than the sun?
The noon is not a luminous body. It simply reflects the sun’s light. At night we see this reflected light, but as the day dawns we see this light less clearly, and as the day gets bright we can not see the moon. The direct rays from the sun outside the rays that are reflected from the moon, light the moon. Actually the moon is very much smaller than the sun. It appears larger because it considerably near to us.
- Why does the sun raise and set? (Seems, it is related to common sense questions but it should be answered according to the important rules of physics)
The earth rotates around its axis once in a day. The portion of elliptic surface of the earth does faces the sun, enjoys what we call daylight and the portion that is away from the sun has the shades of night. To us, it appears that the sun rises, and sets, although it is the earth that rotates round its own axis in front of the sun.
- Why is a winter day in Pakistan shorter than a summer day?
The earth moves round the sun in more or less elliptical orbit. It completes the rotation in one year. The earth also moves simultaneously round its own axis once a day. The axis about which the earth rotates is not perpendicular to the plane in which it moves round the sun, but it is inclined at angle of sixty six and half degrees.
The northern hemisphere, in which Pakistan lies, is a little away from the sun in winter and the sun is shorter above the horizon than in summer. In summer days the sun is longer above the horizon than in winter. That is to say, winter days in Pakistan are shorter than summer days.
These were the most important questions of physics which we have answered briefly. Hope, it will help you out.