To determine the total load on the lintel, let's analyze the possible choices, particularly focusing on the correct option.

**Analysis**:

1. The correct option is defined as the weight of brickwork contained within an equilateral triangle of side L and the load between lintel and slab.
2. This is a common method used in structural engineering to estimate the load on a lintel.
3. The equilateral triangle has an angle of 60° at the vertex, which is typically used to distribute the load above the opening evenly.

**Justification**:

1. The lintel load includes the triangular portion of the wall, depicting how the load disperses at a 45-degree angle downwards.
2. The brickwork that contributes to the lintel load forms this equilateral triangle, which provides stability and distributes the weight properly over the lintel.

**Conclusion**:

1. The load from above transfers down to the lintel as if the brickwork is contained in this triangular configuration.

**Rejection of Other Options**:

• A rectangle whose height is equal to the effective span: This does not correctly represent the distribution of forces.
• A rectangle whose height is equal to the height of the slab above lintel: Does not account for the angle of load distribution.
• A rectangle whose height is equal to the height of the wall above the lintel: Does not represent the triangular load distribution.