Table 1.

Physical parameters and their description.

Symbol	Unit	Description
$$H\left(t\right)$$	W/m2	Input heating function from the absorption of EM energy
$${\displaystyle \hat{H}}$$	W	Power absorption magnitude
$$a$$	m2	Area of the thin film
$${\beta }_0$$	W/(m2 K)	Rate of heat loss per unit area of the film due to conduction, convection, and radiation
$$T_f$$	K	Temperature of the thin film above its surrounding medium
$${{\displaystyle \hat{T}}}_f$$	K	Temperature wave magnitude
$$Q_0$$	W/m2	Heat flow per unit area to the surrounding medium
$$c_s$$	J/(m2 K)	Heat capacity per unit area of thin film
$$T$$	K	Temperature of surrounding medium
$$\alpha$$	m2/s	Thermal diffusivity of the medium
$$\kappa$$	W/(m K)	Thermal conductivity of the medium
$$\beta$$	K−1	Thermal expansion coefficient
$$v$$	m/s	Particle velocity of the medium
$$\psi$$	m2/s	Velocity potential
$$x$$	m	Distance between the source and detector
$${\rho }_0$$	kg/m3	Density of the medium
$$c_p$$	J/(m3 K)	Volumetric heat capacity of the medium
$$v_s$$	m/s	Acoustic velocity of the medium
$$\eta ,\xi$$	cP	Viscosity of the medium
$$d_t$$	m	Thickness of the film