Acoustooptic beam deflector. Consider an acoustooptic beam deflector. The incidence angle θ1 remains fixed, while the acoustic frequency is varied to control the deflection angle θ2. Derive a formula that predicts the maximum useful deflection angle, defined arbitrarily to be that deflection angle for which the diffraction efficiency drops to 50% of its maximum value. Evaluate this formula numerically for the case treated following Eq. (8.4.26), where