This group is called “noble gases” because they do not react with other elements. This is because they have a full valence shell.
Answer:
x = 5[km]
Explanation:
We must convert the time from minutes to hours.
![t=30[min]*\frac{1h}{60min}= 0.5[h]\\](https://tex.z-dn.net/?f=t%3D30%5Bmin%5D%2A%5Cfrac%7B1h%7D%7B60min%7D%3D%200.5%5Bh%5D%5C%5C)
We know that speed is defined as the relationship between space and time.

where:
x = space [m]
t = time = 0.5 [h]
v = velocity [m/s]
Now replacing:
![x = 10[\frac{km}{h} ]*0.5[h]\\x=5[km]](https://tex.z-dn.net/?f=x%20%3D%2010%5B%5Cfrac%7Bkm%7D%7Bh%7D%20%5D%2A0.5%5Bh%5D%5C%5Cx%3D5%5Bkm%5D)
Answer:
C) rift valley
Explanation:
A rift valley is a lowland region formed by the interaction of Earth's tectonic plates. This small rift valley has a typical formation—long, narrow, and deep. It was formed by the Thingvellir rift, where the North American and Eurasian tectonic plates are tearing, or rifting, apart over a hotspot on the island of Iceland.
<u>Answer :</u>
(a) d = 0.25 m
(b) d = 0.5 m
<u>Explanation :</u>
It is given that,
Frequency of sound waves, f = 686 Hz
Speed of sound wave at
is, v = 343 m/s
(1) Perfectly destructive interference occurs when the path difference is half integral multiple of wavelength i.e.
........(1)
Velocity of sound wave is given by :




Hence, when the speakers are in phase the smallest distance between the speakers for which the interference of the sound waves is perfectly destructive is 0.25 m.
(2) For constructive interference, the path difference is integral multiple of wavelengths i.e.
( n = integers )
Let n = 1
So, 


Hence, the smallest distance between the speakers for which the interference of the sound waves is maximum constructive is 0.5 m.