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The term period (symbol: T) describes the time it takes for an object to complete one full cycle of motion on a spring.
The formula for time is: T = 1 / f , where f is the frequency , f= c / λ = wave speed c (m/s) / wavelength λ (m)..
The formula describes that as the frequency of a wave increases, the time period of the wave decreases.
The refractive index is used to measure how much light bends as it goes from one medium to another the refractive index of air =1 as light doesn’t bend in it
When looking into a glass of water with a straw the straw may appear bent or morphed as the water has a different refractive index to air (and the light is passing from air to glass of water)
Answer:
Mg (atomic number 12)
K (atomic number 19)
Explanation:
The size of an atom is estimated in terms of its atomic radius.
The atomic radius is taken as half of the inter-nuclear distance between two covalently bonded atoms of non-metallic elements or half of the distance (d) between two nuclei in the solid - state of metals.
- Across a period, atomic radii decrease progressively from left to right.
- This is due to the progressive increase in the nuclear charge without increase in the number of electronic shells.
- Down a group, atomic radii increase progressively due to the successive shells of electrons being added which have been compensated for by the increase in nuclear charge.
Cl is further right of Mg in the third period
K is below Na in the first group
Mechanical waves need material stuff to travel through.
They cannot travel through vacuum.
That's why we can't hear the explosions on the sun.
That's also why astronauts standing on the moon or working outside the Space Station have to use radio to talk to each other, even if they're only a few inches apart. There's no air between them, or any other material stuff. So sound can't travel between them.
