Answer:
1) f= 8.6 GHz
2) t= 0.2 ms
Explanation:
1)
- Since microwaves are electromagnetic waves, they move at the same speed as the light in vacuum, i.e. 3*10⁸ m/s.
- There exists a fixed relationship between the frequency (f) , the wavelength (λ) and the propagation speed in any wave, as follows:

- Replacing by the givens, and solving for f, we get:

⇒ f = 8.6 Ghz (with two significative figures)
2)
- Assuming that the microwaves travel at a constant speed in a straight line (behaving like rays) , we can apply the definition of average velocity, as follows:
where v= c= speed of light in vacuum = 3*10⁸ m/s
d= distance between mountaintops = 52 km = 52*10³ m

⇒ t = 0.2 ms (with two significative figures)
The answer is c) RNA contains uracil and ribose.
Answer:
Explanation: P = 300 W and t = 2 min = 120 s
Energy Q = Pt = 300 W · 120 s = 36 000 J.
Thus, plate can not produce 45 000 J heat.
Answer:

Explanation:
Let the distance moved by Joe is "d"
so the time taken by him to drove it by speed 45 mph is given as


now the same distance is traveled by him with speed 55 mph
so the time taken by him

so total time taken by him for complete distance 2d



now the average speed is given as


