Answer:
Frequency, f = 0.6 Hz
Explanation:
We have,
Number of waves passing through a point are 3
Time for which the waves are passing is 5 seconds
It is required to find the frequency of a wave. The frequency of a wave is defined as the no of waves per unit time. So,

So, the frequency of a wave is 0.6 Hz.
Answer:
212.8 dm^3 or L
Explanation:
1 mole of any sub=6.02×10^23 molecules
X mole of O2=5.7×10^24 molecules
X mole=5.7×10^24/6.02×10^23
=9.5 mole
1 mole of any gas at stp=22.4 dm^3
Therefore, 9.5 mole of O2 will be 22.4×9.5
=212.8 dm^3
The 4th energy level (row), 's' orbital block, 2nd group (column). The valence electrons are found in the highest energy level of the electron configuration in the 's' and 'p' orbitals. In the case of calcium this is 4s2 . This gives calcium an 's' orbital with a pair of electrons in its valence shell
Density=mass/volume
Density=18.4g/11.2ml
Density=1.64
Just make sure you include the unit of measurement with your answer.