Answer:
Helium has many unique properties: low boiling point, low density, low solubility, high thermal conductivity and inertness, so it is use for any application which can exploit these properties. Helium was the first gas used for filling balloons and dirigibles.
Multi cellular organisms are composed of many cells whereas unicellular organisms are composed of single cell. Multicellularity is indeed a progressive attribute of evolution where cells form tissue which forms organ and then organ system and finally an organism. Both multi cellular and unicellular organisms has advantages and disadvantages of their own. One of the main disadvantage of multi cellular organisms is that due to such a complex composition and functioning they require a large amount of energy for their maintenance and survival. Different organs and system require a huge amount of energy when it comes to comparison with unicellular organisms. A large amount of energy is also wasted in all these life processes. Though multi cellular organisms can survive in a variety of environmental conditions but then also their survival is difficult than any unicellular organism.
Answer:
a) Its called Doppler shift effect
b) It gets compressed
c) It gets stretched
d) The pitch of a wailing ambulance is high as it approaches you and gets lower as it moves away from you
Explanation:
It is observable even in space. The galaxies that are moving away from us appear in the red-shift while galaxies that are moving towards us appear in the blue shift.
To begin with, remember that the blue wavelength of light is of a shorter wavelength while the red light is of a longer wavelength. An every day scenario of Doppler shift is that of a wailing ambulance approaching you then going past you. As the ambulance approaches you, the pitch of its wailing is high but when it passes you and moves away from you the pitch gets lower.
This is because of the changes in the relative wavelength of the wave. As the object moves towards you, the waves tend to be ‘compressed’, relative to your position, into a slightly smaller wavelength. As the object moves away, the wave tends to be stretched, relative to your position, hence the wave acquires a longer wavelength.
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The liquid contains only one element, therefore - the liquid is a pure substance