Answer:
No Refraction takes places
Explanation:
When light travels from one medium to another at an angle of incidence 0 degree then no refraction takes place .
It is because according to Refraction law
sini = 
sinr
where 
are the refractive index of medium of incidence and medium of refraction .
When i = 0 , left side of the equation becomes 0 and thus r (angle of refraction) must be zero. So No refraction takes place
Answer:
hi how are you doing today Jasmine
Index fossils are used to determine the relative ages of rock and fossils and are also used to define the boundaries between geologic periods.
<u>Option: A</u>
<u>Explanation:</u>
The fossils which are recognized as fossils guides or indicator fossils are used to classify and recognize geological or faunal periods, termed as index fossils. It must be of short vertical reach, wide geographic distribution and swift patterns in evolution. It helps to assess the rock layers ' age and helps to date other fossils found close and around them. For an instance, Ammonites were abundant in the Mesozoic period between 245 to 65 mya, they have not been found after the Cretaceous era, as they became endangered during the K-T extinction (65 mya).
Ionic compounds is your answer. What happens is one atom donates electron(s) to the other atom, making one positive and the other negative. The opposite atoms attract, forming an ionic bond.
Hope this helps! :)
