A) Define Work, Energy and Power. (b) A crane lifts a load of mass 500 kg through a height of 15 m in 25 s.

        Wavelength $\lambda = 0.80 \text{ m}$  
        Frequency $f = 250 \text{ Hz}$

        $$
        v = f\lambda
        $$

        $$
        v = (250 \text{ Hz}) \times (0.80 \text{ m})
        $$
        $$
        v = 200 \text{ m/s}
        $$
        The wave speed is $\boxed{\text{200 m/s}}$.

    *   **(ii) Calculate time period.**

        Frequency $f = 250 \text{ Hz}$

        $$
        T = \frac{1}{f}
        $$

        $$
        T = \frac{1}{250 \text{ Hz}}
        $$
        $$
        T = 0.004 \text{ s}
        $$
        The time period is $\boxed{\text{0.004 s}}$.

*   **c)** **Resonance** is a phenomenon that occurs when an oscillating system is driven by an external force at its natural frequency, resulting in a significant increase in the amplitude of oscillations.

*   **d)** Four properties common to all waves are:
    1.  **Reflection**
    2.  **Refraction**
    3.  **Diffraction**
    4.  **Interference**