Answer:
A
Explanation:
<em>The gold used in the making of jewelry is usually not pure but a heterogeneous mixture of metals. Pure gold is quite soft and even though it may look better in appearance compared to those made using heterogeneous mixtures, it usually bends easily. Hence, in order to make the jewelry more durable, gold is usually mixed with other metals to form a heterogeneous mixture. </em>
The correct option is A.
-- The unit of frequency is "per second" (Hz), which is [reciprocal time].
-- The unit of period is "second", which is [time].
Do you see where this is going ?
'Frequency' and 'period' are reciprocals of each other.
For any wave ...
Period = (1) / (frequency) .
Frequency = (1) / (period) .
Answer:
Continental drift theory describes the long term effect of plate tectonics.
Explanation:
The long term result of plate tectonic movement is the continental drift. The continents of Earth lay on tectonic plates, that are in motion and interaction via plate tectonics. The drift of the Earths continent is an ongoing process evident in the rift valleys and seafloor spreading zones.
The theory that the Earth's continents are dynamic and have drifted relative to each other is known as continental drift which correlates with the theory of plate tectonics.
Every year, the Earth's outer shell plates are displaced by a small amount due to the heat coming from the Earths interior via convection currents.
Answer:
finding Cepheid variable and measuring their periods.
Explanation:
This method is called finding Cepheid variable and measuring their periods.
Cepheid variable is actually a type of star that has a radial pulsation having a varying brightness and diameter. This change in brightness is very well defined having a period and amplitude.
A potent clear link between the luminosity and pulsation period of a Cepheid variable developed Cepheids as an important determinants of cosmic criteria for scaling galactic and extra galactic distances. Henrietta Swan Leavitt revealed this robust feature of conventional Cepheid in 1908 after observing thousands of variable stars in the Magellanic Clouds. This in fact turn, by making comparisons its established luminosity to its measured brightness, allows one to evaluate the distance to the star.
There's no such thing as "stationary in space". But if the distance
between the Earth and some stars is not changing, then (A) w<span>avelengths
measured here would match the actual wavelengths emitted from these
stars. </span><span>
</span><span>If a star is moving toward us in space, then (A) Wavelengths measured
would be shorter than the actual wavelengths emitted from that star.
</span>In order to decide what's actually happening, and how that star is moving,
the trick is: How do we know the actual wavelengths the star emitted ?
