- Why does the tilt of the Earth’s axis relative to its orbit cause the seasons as the Earth revolves around the Sun? Draw a diagram to illustrate your answer.
Earth's seasons are the result of the tilt of the Earth's axis. Since the axis is tilted, different parts of the globe are oriented towards the Sun at different times of the year. Summer in the Northern Hemisphere is warmer than winter as the Sun's rays hit the Earth at a comparatively more direct angle for larger portions of the day, producing more heat and vice versa. Due to this very same tilt, when the Sun crosses the Equator it causes the equinoxes.
- Where do you have to be on the Earth to see the Sun at your zenith? If you stay at one such location for a full year, on how many days will the Sun pass through the zenith?
To see the Sun at its Zenith a person can be at a place between 23.5o N (The Tropic of Cancer) and 23.5o S (The Tropic of Capricorn). The sun passes it Zenith twice between these two latitudes twice a year and once every year on these latitudes.
- What are the synodic and sidereal periods of a planet?
Sidereal time is the time taken by a planet to orbit round the sun and is measured by the relative position of the planet with the focal star in accordance with stars in the background. Synodic time is the time between successive sun earth planet alignments known as superior junctions (UNL).
- Why does an astronaut have to exert a force on a weightless object to move it?
An astronaut needs to exert force on a weightless body because movement depends upon the momentum of the body and its inertia, which is decided by its inertial mass and not its gravitational mass. To bring a body into motion force must be applied, which changes its inertia from rest to motion
- What are the three major functions of a telescope?
- Increase the total amount of gathered light energy so as to make objects visibly brighter and clearer
- Increase angular resolution of the observed object
- Magnify the image of the object
- Compare an optical reflecting telescope to a radio telescope. What do they have in common? How are they different?
The similarity between these two telescopes is that both use Electro-magnetic radiations for observation and curved reflecting surfaces to focus incident radiations. The difference between is that optical reflecting telescope operates at visible light range and uses a thin reflective coating and a smaller diameter of receiving surface while Radio frequencies are used for the operation of Radio telescope which employs larger metal dishes as reflecting surfaces.
- Using Wien’s law and the Stefan-Boltzmann law, explain the changes in color and intensity that are observed as the temperature of a hot, glowing object increases.
Wien’s law says that as light emitting objects get hotter, their dominant wavelength decreases from Infrared to red and the rest of the visible spectrum. Stefan-Boltzmann law propounds that more the temperature of the object higher is the intensity of radiations, presuming that the visual diameter remains constant. This means that larger illuminating objects may appear brighter even when they are cooler than their smaller counter parts.
- Why do different elements have different patterns of lines in their spectra?
Different elements have different number of electrons (subatomic particles) orbiting at different energy levels. Patterns of absorption or emission spectra of photons for different elements are determined different transition energy levels of these electronic orbits. This means that all elements would produce photons of frequency and wavelengths unique to them, creating unique spectrum for each element.
Panebieanco, D. Wiens Law and Stefan-Boltzmann law. 2007. Independent Research.
UNL. Sidereal and Synodic Periods. 2012. UNL Astronomy