How it can be proved that the basic structure of the modern periodic table is based on the electronic configuration of atoms of different elements?

Draw ray diagrams each showing:Hypermetropic eye.

Name the defect which is caused when a person’s eye lens hardens.

When we place a glass prism in the path of a narrow beam of white light a spectrum is obtained. What happens when a second identical prism is placed in an inverted position with respect to the first prism? Draw a labelled ray diagram to illustrate it.

The electronic configuration of an element is 2, 8, 4. State its:

1. Group and period in the modern periodic table.
2. Name and write its one physical property.

Why do stars twinkle?

What changes take place in the shape of eye-lens:

1. When the eye is focused on a near object?
2. When the eye is focused on a distant object?

Why does the sky appear dark instead of blue to an astronaut?

Why does the sky appear blue on a clear day?

Explain why, we cannot see our seats first when we enter a darkened cinema hall from bright light but gradually they become visible.