Give two advantages that a telescope lens or mirror of large diameter has over one of small diameter
The light-gathering power of an optical telescope is directly related to the diameter (or aperture) of the objective lens or mirror. Note that the area of a circle is proportional to the square of the radius. A telescope with a lens which has a diameter three times that of another will have nine times the light-gathering power. Larger objectives gather more light, and more sensitive imaging equipment can produce better images from less light.
Source:
http://en.wikipedia.org/wiki/Optical_telescope
what are the similarities and differences among the isotopes of an element?
To understand the similarities and differences among the isotopes of an element, let's first define what isotopes are. Isotopes are atoms of the same element that have different numbers of neutrons in their nuclei. This means they have the same number of protons (which defines the element) but different numbers of neutrons.
Similarities among isotopes:
1. Isotopes of the same element have the same number of protons, which determines the element's atomic number and its chemical properties.
2. Isotopes have similar electron configurations, which means their outermost electron shells are arranged in a similar way. This affects the way they participate in chemical reactions.
Differences among isotopes:
1. Isotopes have different atomic masses due to having different numbers of neutrons. The atomic mass is the total number of protons and neutrons in the nucleus.
2. Isotopes may exhibit different stability. Some isotopes are stable and do not decay over time, while others may be unstable and undergo radioactive decay.
3. Isotopes may have different physical properties. For example, isotopes of hydrogen have different nuclear spins, resulting in different magnetic properties.
4. Isotopes can have different uses in various fields. For instance, certain isotopes are used in radioactive dating, nuclear medicine, or nuclear power.
To determine the similarities and differences among the isotopes of a specific element, you can refer to the periodic table to find the number of protons (atomic number) and the average atomic mass of each isotope. This information will help you identify the similarities and differences in terms of atomic structure, stability, and other properties specific to the element's isotopes.