A standing wave also known as a stationary wave, is a wave in which its peaks or any other point on the wave do not move spatially.

This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite directions. The most common cause of standing waves is the phenomenon of resonance, in which standing waves occur inside a resonator due to interference between waves reflected back and forth at the resonator's resonant frequency.

Hence, standing wave occurs when a wave reflects upon itself.

Except Rock color, all other Graded bedding, Ripple marks and Mud cracks are sedimentary structures.

The aim of a group or party must be

• The mission or purpose of the group - what business they are in.

• The vision or direction they are headed - often expressed as the impact they want to have distinct from their purpose. 

• The strategies for how they will get from where they are today to where they are headed; these are broadly stated, like a 50,000-foot overview, and are typically few in number, usually no more than 3-5 key areas of focus. 

• The goals and objectives for how the strategies will be implemented; these are sometimes referred to as tactics or operational plans; there is usually no specific limit on the number of these, and they are more specific and not so far out in the future, often 1-2 years or less.

The given number series is 

3, 5, 8, 15, 28, 51, ?

Here the pattern it follows is

3

3 + 2 = 5 ( add prime number less than 3 i.e, 2)

5 + 3 = 8 (3 is prime number less than 5)

8 + 7 = 15 (7 is prime number less than 8)

15 + 13 = 28 (13 is prime number less than 15)

28 + 23 = 51 (23 is prime number less than 28)

51 + 47 = 98 (47 is prime number less than 51)

Hence, the next number in the given number series is 98.

An electric arc is a visible plasma discharge between two electrodes that is caused by electrical current ionizing gasses in the air. Electric arcs occur in nature in the form of lightning.

The given statement about similar triangles is TRUE.

Similar Triangles Theorem :: Similar triangles are two triangles with corresponding angles of equal measure, and the ratios of their corresponding sides' lengths are equal.