Which of the following scales are not linear in nature?
(i) Decibel
(ii) Richter
(iii) Meter

Options

A. (i) only
B. (ii) and (iii)
C. (ii) only
D. (i) and (ii)

Explanation

To determine which of the following scales are not linear in nature, we will analyze each option provided: Decibel, Richter, and Meter.

### Step-by-Step Solution:

1. **Understanding the Decibel Scale:**
- The decibel (dB) scale is a logarithmic unit used to express the ratio of power or intensity of two values.
- Since it is logarithmic, it does not increase linearly; for example, an increase of 10 dB represents a tenfold increase in intensity, not a simple addition.
- **Conclusion:** The decibel scale is not linear.

2. **Understanding the Richter Scale:**
- The Richter scale is also a logarithmic scale used to measure the magnitude of earthquakes.
- Similar to the decibel scale, each whole number increase on the Richter scale represents a tenfold increase in measured amplitude and approximately 31.6 times more energy release.
- **Conclusion:** The Richter scale is not linear.

3. **Understanding the Meter Scale:**
- The meter is a standard unit of length in the metric system.
- It is a linear scale, meaning that equal increments on the meter scale represent equal distances. For example, 1 meter is always 1 meter, regardless of where you are on the scale.
- **Conclusion:** The meter scale is linear.

4. **Final Evaluation:**
- From our analysis, we find that both the decibel and Richter scales are not linear, while the meter scale is linear.
- Therefore, the scales that are not linear in nature are the Decibel and Richter scales.

### Answer:
The scales that are not linear in nature are:
- (i) Decibel
- (ii) Richter

Thus, the correct option is **4 (i and ii)**.

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