Which of these methods involves the observation of red shift and blue shift to measure accurately the distance from earth to the stars?
a) blue shift
b) hr diagram
c) doppler effect
d) parallax method

The correct answer is C. The Doppler Effect involves the observation of red shift and blue shift to measure accurately the distance from Earth to the stars.

Explanation:

The Doppler effect, named after the Austrian physicist Christian Andreas Doppler, is the change in apparent frequency of a wave produced by the relative movement of the source with respect to its observer.

In the case of the visible spectrum of electromagnetic radiation, if the object moves away, its light shifts to longer wavelengths, producing a shift towards red. If the object approaches, its light has a shorter wavelength, moving towards blue. This deviation to red or blue is very slight even at high speeds, such as relative speeds between stars or between galaxies, and the human eye cannot capture it, only measure it indirectly using precision instruments such as spectrometers. If the emitting object moved to significant fractions of the speed of light, the wavelength variation would be directly visible.

water is a polar molecule. a chemical bond is a force of attraction between atoms or ions. bonds form when atoms share or transfer valence electrons. atoms form chemical bonds to achieve a full outer energy level, which is the most stable arrangement of electrons. so, false

explanation:

in h2o molecule, two water molecules are bonded by a hydrogen bond but the bond between two h - o bonds within a water molecule are covalent. the greater the electronegativity difference, the more ionic the bond is. bonds that are partly ionic are called polar covalent bonds. nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegativities of the two atoms are equal.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.