Answer: The orbital speeds of stars far from the galactic center are surprisingly high.
Dark matter is a type of matter, whose composition is unknown and which corresponds to 80% of the matter in the universe. Its name refers to the fact it does not emit or interact with any type of electromagnetic radiation, being completely transparent throughout the electromagnetic spectrum.
<h2>However,
it interacts with the known matter through gravity. </h2><h2 />
In this sense, it is believed that the Milky Way has 90% dark matter and only 10% ordinary matter (known matter). Because, like gravity, dark matter can not be observed directly, however its existence is inferred through the movement of the stars far from the center and the cosmic dust within the galaxy.
The speed of sound in a solid would be 6000 metres per second
Answer: 53.4 kJ
Explanation:
Exothermic reactions are defined as the reactions in which energy of the product is lesser than the energy of the reactants. The total energy is released in the form of heat and for the reaction comes out to be negative.
To calculate the moles of sodium , we use the equation:
According to stoichiometry, it can be seen that :
2 moles of sodium will liberate = 822 kJ
Thus 0.13 moles of sodium will liberate =
Thus 53.4 kJ of heat is released if 2.972 g of Na are consumed in the reaction.
Answer:
The index of refraction of the first medium must be higher than the index of refraction of the second medium
Explanation:
Snell's law describes the behaviour of light at the boundary between two mediums:
where
n1 and n2 are the index of refraction of the two mediums
are the angle between the direction of the light ray and the normal to the interface
We can rewrite the condition as:
Let's assume now that the light is travelling in the first medium with a very large angle with respect to the normal to the surface, i.e. , so that . In this case, we have
We notice that if , the ratio on the right is larger than 1, and so the term should be also larger than 1: but this is not possible of course, since the sine function is always less than 1. Therefore, in this case total internal reflection occurs, because no refracted ray is produced.
Answer:
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Explanation: